yeah but he already said he has no cash to bribe CS'es or buy votes which probably also means he cant propose. Unless he gets really lucky neither embargo is going to be lifted. The conquering/razing and selling buildings strategy is solid IF you still have the units left for conquest. You may want to try loading an old autosave? It does suck but you seem to be in a tough spot
If it is early WC, then there are not so many votes to begin with and CS do have quests, many of them are quit influence heavy.
He said he had -100 gpt, you don't have -100 gpt unless you have a lot of units. I lost all my trade routes in a war once and didn't go -100 gpt (I got -40ish, with fairly good amount of units), so to have -100 gpt, he has units.
If it is late WC, then it is more problematic, but there are choices in the ideologies that helps.
If isolated:
* Have a scarce but decent net of roads so you get city connection gold. This also needs you cities to be large, but since you are isolated - food caravans, especially to the capital.
* Change focus in the cities, not in all perhaps, but in the ones that matter.
* If not at war, reduce size of your army, keep only the highly promoted ones. If at war, it is not that hard to pillage and loot (even without the honour finisher) so you keep afloat (so try to move the war to them). With the honour finisher, it is easier.
* Try to get your way into the game again. Doing quests for CSs. Try trade luxuries for money, even if it is not huge (due to the fact that the AI hate you. I once traded my incense for 2-5 gpt each, not much perhaps, but it was to 7 AIs and also I got a diplo-hit (traded recently) with each of them.
* If you manage to get to propose, try to propose to lift the CS embargo and then try to bribe an AI with some resources to vote for this (just to make sure that they do).
* Insert your own idea here ...