Those are my responses:
1. NO: This building in theory is an amazing building. Being able to trade and interact with other players is the point of multiplayer game. I understand that it can be abused, and it is being abused, but removing it completely would be a grave mistake.
I suggest removing the ability to buy troops with gold, so you can only buy troops with resources, this way abuse would be a lot less possible. (but it would still have negative effects on players using it as intended).
best fix would be a crackdown on players who "cheat" with it (aka. bank accounts)
2.A: NO, with a but:
The miracles are an example how not to implement multiplayer feature. since 1 player can basically ruin the miracle for all players on island. currently you need 1 priest for every 4 citizens to keep faith on 100% this means that every player needs to keep 20% of their population as priests. Perhaps there should be an increased effect of conversion % in your city and island share of your town.
For example: if there are 10 identical players on island and each has 100% conversion in their cities so each one contributes 10% to island share (for total 100%). i would change that every player on island adds an imaginary +10% to the max island share. in our example with 10 identical players each player faith would contribute 10% of total 190%. now each player will contribute 19% of island instead of previous 10%. this means that individual priests are stronger if more people use temple. and shutting down whole island with multis would be less effective.
of course the numbers and % could be changed, but the idea is still valid.
2.B: YES, with if:
I would personally suggest to change Hephaestus (since it is by far the most popular god), so it provides more armour, and change Ares to provide more damage.
or you could change Ares to be more similar to Hephaestus and provide boost only for naval units.
shortening round times would be a big no from me
3. BIG NO:
Your numbers are wayyy too high. A player producing 10.000 gold per hour (quite a lot) would earn around 88 million in full year. so with your suggestion you could get decades worth of gold with a single purchase.
Also resource/gold packs staying the same regardless of your score is for a reason. so that the game don't became pay to win. with current resources packs it is quite good in early stages if you want to progress fast, with diminishing returns. in late game your production becomes more important and you switch to boosting it with ambrosia instead of buying resources outright.
Don't mean to be rude, but those suggestions have been one of the worst i have seen in a while. I agree with you on some points, but implementing others would be disaster.