Wow, there's a ton of information here, thanks Archduke!
I'll just toss out a few thoughts for right now and I'll probably have more later.
* I'm not sure why Greece is so opposed to you despite having no contact for the first 80-90% of the game. If Kaiser's determined to be opposed though, then you'll just have to keep doing what you've been doing, work around him as best you can. The biggest thing that Russia needs to defend is getting at least one cossack out on the field. The instant that one of those units appears, every city's defensive rating shoots up to about 60 and Greece can never capture a city under any circumstances. (I don't see horses and phalanxes doing much against crossbow-defended cities packing Defender of the Faith either but cossacks make attacking impossible.) Stall for the moment and look to counterattack in 10-15 turns. Do not declare war, let him make the first move and attack into your defenses.
* Have you reached out to Cornflakes at all? He's your obvious ally if there's a Cree + Greece alliance. Try seeing if you can get him on your side moving forward. Anything he can do to tie down Cree/Greek units would be a major help.
* TBS: Russia has effectively equal science/culture with the Cree but that gold/turn income is downright scary. Do you know how he's been able to accumulate so much wealth? It's too bad that Russia wasn't able to save up more money while pushing towards cossacks but that's water under the bridge now. I still do not think it's a good idea to try attacking TBS, his cities will be much better defended and I don't see cossacks making much progress. That's in contrast to Greece where the cities have 26 (!) defensive rating. Cossacks would slice through Greek cities like a hot knife through butter. I would defend in the south and attack in the east, not the other way around, and force TBS to come attack you. No, you can't defend your coastal cities again a determined frigate attack but almost all of your cities are inland. If you lost Radio + Spice Melange while taking every Greek city... well, that's a net positive as far as I can see. I just don't think your plan for a raid on TBS will work. And heck, if you can get your cities up to 60 defensive rating, you might actually be able to hold out OK against frigates, long enough to tech to them yourself.
* Mahabodi Temple: did you pick the new religious beliefs yet? I'd suggest Tithe and Wats if they're still available. You're probably not spending faith on Wats right now but at least that denies them to anyone else.
* Did the new Golden Age start yet? Continuing Monumentality for the next 30 turns feels like a no-brainer.
* Fogger: you need to swap Fogger over to the Grandmaster's Chapel if you haven't done so already. (It was not switched over in the posted screenshot.) This is not pre-expansion Civ6, you must have the Grandmaster's Chapel finished to faith purchase units, and Fogger is the only city that can build it. The tier 2 government building requires having a tier 2 government which Russia just adopted this turn in Monarchy. The sooner you start the Grandmaster's Chapel, the sooner it will be done. If you have a spare builder charge or two sitting around, I'd burn forest chops to get it done faster. (The forest east of the southern Encampment could surely be sacrificed here.)
* Last thought: very glad to see the missonary incoming to Ownage for Defender of the Faith. The new city in the north will need religion too for the second charge, and perhaps you'll be able to get more spreads inside Greek cities later. I really don't see how Kaiser can attack you with any success, or how he defends against a push from cossacks later. I mean, cossacks are 67 strength, +5 strength if they're in your territory from DOTF, another +5 strength in your territory or within one tile from their natural unit bonus. That's 77 strength (!!!) units when defending your territory. Against a horseman (36 strength), you would deal an average of 145 damage and take an average of 6 damage. Yikes. Oh, and the cossacks can move after attacking to walk back to safety. How could he ever stop you from running over his cities? Just get half a dozen of them and a battering ram to take down walls and it's a GG situation for sure.