Okay, here are some more thoughts along the lines of Stonehenge. The wonder itself seems fairly easy for us to get once it's available - the bigger issue concerns how we slot Mysticism somewhere into the tech programme.
- The earliest we can possibly make a bid for Stonehenge (that wouldn't be downright silly, as in going for Mysticism straight out of the gate) would be by going Hunting (7) -> Mysticism (16). Pros: We can finish Stonehenge around turn 27/28 (!). Cons: We only get one extra Warrior out, delays a second Worker until the early 30's (!), delays our first Settler until the early 40's (!), delays either AH until turn 28 and BW until turn 52/53 (!) or BW until turn 41/42 and AH until turn ~54 (!). Overall: Not good.
- The next-quickest option would be to go Hunting (7) -> AH (19/20) -> Mysticism (27/28 ), and go straight for Stonehenge when Mysticism comes. Pros: We get the second Worker (22) and 3-4 extra Warriors built by the time Mysticism comes, then Stonehenge arrives at turn 35/36. Cons: Delays our first Settler until the early 40's (!), delays BW until turn ~52 (!). Overall: Okay, but not stellar by any means.
- There's an interesting slight variation of the above option, building a Settler instead of 2-3 more Warriors while waiting for Mysticism to arrive. Pros: Get the second Worker on schedule (22), an early first Settler (31), and Stonehenge at turn 40/41. Cons: Only build 1 extra Warrior, initial growth curve messed up from being at size 2 until turn 35, next Settler not available until mid 40's (!), delays BW until turn ~52 (!). Overall: A little better but still not great. Might work better with BW before AH, since we'd be at size 2 for so long in this case.
- Another variant of the Hunting -> AH -> Mysticism case would be to build Warriors until size 3, then the first Settler as planned, then Stonehenge. Pros: Gets second Worker (22), 3 extra Warriors, reasonably early first Settler (33), and Stonehenge is built at turn 40/41 (maybe 39). Cons: Next Settler not available until mid 40's (!), delays BW until turn ~51 (!). Overall: Seems like the best of the available options if we want to grab Stonehenge pre-turn 50. Essentially we continue with our previous plan until turn 33, then switch to Stonehenge and delay cities #3 and beyond (as well as delaying chop access for an extra 7 turns compared to not getting Mysticism).
I don't see a lot of logic in going Hunting -> AH -> Mining -> Mysticism or Hunting -> Mining -> Mysticism, so I think the above are pretty much all the reasonable options we have for going at Stonehenge early.
Aside from those options, the only thing that's left is grabbing Mysticism around turn 52-53 (after the "big 4" starting techs) and chopping Stonehenge out at 53-55. This has the obvious advantage that it doesn't stunt our early growth, so we'd probably have at least 3-4 cities to immediately benefit from the wonder as soon as it arrived. However, the major disadvantage is that waiting an extra ~15 turns (compared to the option in the above paragraph) may well see the wonder taken by someone else. There's a big difference between turn 40 (2400 BC) and turn 55 (1800 BC) when you're talking about Stonehenge, after all.
Senseless, I'd welcome any thoughts or opinions you have on the various simulations for Stonehenge (or any mistakes you can point out in my calculations). Maybe you can suggest something I've missed that might be a better alternative as well.
One random unrelated thought I just had on the AH vs BW matter: you know, going AH-BW does give the tiny, tiny potential advantage that it gives slightly more time for additional forests to spawn near our capital before we chop the existing ones down.
Of course, this is so unlikely that it's not worth banking on, but I figured I'd put it on the table for completeness anyway. 
- The earliest we can possibly make a bid for Stonehenge (that wouldn't be downright silly, as in going for Mysticism straight out of the gate) would be by going Hunting (7) -> Mysticism (16). Pros: We can finish Stonehenge around turn 27/28 (!). Cons: We only get one extra Warrior out, delays a second Worker until the early 30's (!), delays our first Settler until the early 40's (!), delays either AH until turn 28 and BW until turn 52/53 (!) or BW until turn 41/42 and AH until turn ~54 (!). Overall: Not good.
- The next-quickest option would be to go Hunting (7) -> AH (19/20) -> Mysticism (27/28 ), and go straight for Stonehenge when Mysticism comes. Pros: We get the second Worker (22) and 3-4 extra Warriors built by the time Mysticism comes, then Stonehenge arrives at turn 35/36. Cons: Delays our first Settler until the early 40's (!), delays BW until turn ~52 (!). Overall: Okay, but not stellar by any means.
- There's an interesting slight variation of the above option, building a Settler instead of 2-3 more Warriors while waiting for Mysticism to arrive. Pros: Get the second Worker on schedule (22), an early first Settler (31), and Stonehenge at turn 40/41. Cons: Only build 1 extra Warrior, initial growth curve messed up from being at size 2 until turn 35, next Settler not available until mid 40's (!), delays BW until turn ~52 (!). Overall: A little better but still not great. Might work better with BW before AH, since we'd be at size 2 for so long in this case.
- Another variant of the Hunting -> AH -> Mysticism case would be to build Warriors until size 3, then the first Settler as planned, then Stonehenge. Pros: Gets second Worker (22), 3 extra Warriors, reasonably early first Settler (33), and Stonehenge is built at turn 40/41 (maybe 39). Cons: Next Settler not available until mid 40's (!), delays BW until turn ~51 (!). Overall: Seems like the best of the available options if we want to grab Stonehenge pre-turn 50. Essentially we continue with our previous plan until turn 33, then switch to Stonehenge and delay cities #3 and beyond (as well as delaying chop access for an extra 7 turns compared to not getting Mysticism).
I don't see a lot of logic in going Hunting -> AH -> Mining -> Mysticism or Hunting -> Mining -> Mysticism, so I think the above are pretty much all the reasonable options we have for going at Stonehenge early.
Aside from those options, the only thing that's left is grabbing Mysticism around turn 52-53 (after the "big 4" starting techs) and chopping Stonehenge out at 53-55. This has the obvious advantage that it doesn't stunt our early growth, so we'd probably have at least 3-4 cities to immediately benefit from the wonder as soon as it arrived. However, the major disadvantage is that waiting an extra ~15 turns (compared to the option in the above paragraph) may well see the wonder taken by someone else. There's a big difference between turn 40 (2400 BC) and turn 55 (1800 BC) when you're talking about Stonehenge, after all.
Senseless, I'd welcome any thoughts or opinions you have on the various simulations for Stonehenge (or any mistakes you can point out in my calculations). Maybe you can suggest something I've missed that might be a better alternative as well.
One random unrelated thought I just had on the AH vs BW matter: you know, going AH-BW does give the tiny, tiny potential advantage that it gives slightly more time for additional forests to spawn near our capital before we chop the existing ones down.
Of course, this is so unlikely that it's not worth banking on, but I figured I'd put it on the table for completeness anyway.