[13lackGu4rd]

1) glaive troops should be used against high protection enemies, mainly heavy infantries. long spears have long range, therefore good repel, so they're best at holding the line against regular short/broad sword infantrymen. Baalz's guide specifically mentions the use horses with hold and attack orders, not fire. that way they fire for 2 turns if in range(so put them towards the front) than attack.

2) it's still possible to discover spies but it should be awfully hard at 200. the most likely scenario I can think of is that the AI started to patrol his capital with a huge army(probably with good patrollers too, anything with patrol bonus, cavalry and fliers are especially good patrollers).

3) order 3 would have really helped, you should have cut somewhere else. what's your production, growth and temperature scales? also, how large are you, with how many forts, etc? usually having a gold shortage in the late game is very odd, but considering that you're mostly using non sacred mages and huge armies, it isn't unheard of. just make sure you have enough forts(especially on high income provinces like farmlands) and that you don't have troops sitting around doing nothing. you can also get some patrollers of your own to extra tax some provinces for a larger income.

4) celestial servants are basically meat shields. they're pretty big so they're a favored target for spells and attack large orders. that's the only reason to ever get them, and it's a good reason. the other summons are better. hounds as you said provide flying support. celestial soldiers are very solid line troops, and are also bigger than your normal infantry.

5) internal alchemy is a very problematic spell, for the reason you mentioned. generally the only reason to use it is if you get some rare randoms on your old mages and for some reason you can't craft an elixir of life or boots of youth for them. insanity at below 10% isn't that bad, though it can still be annoying from time to time, more than that and it's really starting to be a pain in the rear. so if you do use it, make sure to not use it too much.

6) every mod has a change log file. that should have everything you're looking for.

7) not sure what your question is, but Baalz' guides, both on MA TC and on communions give a ton of very useful information on them. "and a few Alkies get killed each battle since they have to be close enough to cast and so get hit by stray arrows" you're doing something wrong here, if your alchemists move forward in order to cast. script them with spells that have longer range, to not risk them like that, it's just not worth it.