Civ game 236 years old

I have been playing a game of Civilization for 236 years now, and have got somewhat stuck.

My country is running out of money, and has a lot of citizens sitting around doing nothing. Production has fallen, I’ve abandoned the space race, and most of my tax revenue goes towards luxuries and maintaining a large military. I’ve tried to increase taxes, but the Senate keeps overruling. Pollution is not too bad at the moment, but there are a few ice cap squares that have melted.

Any suggestions? I’ve thought about a military victory, but all the major AIs have nukes, so I’m reluctant to do that. Should I be changing governmental type?

Thanks in advance.

(See playing same civ game for 10 years)