Supervisor demanding impossible workload at the very end of my PhD. Considering change of supervisor
I agree with user Maarten Buis that this is probably too personal to really give good advice. But let me suggest a few things. 

You should probably optimize everything now for quick completion of your degree under a situation over which you have little control. 

While you can ask your supervisor for more funding, he has already said no. What has changed to make him say yes?

While you can complain to the institute that would most likely result in animosity from your advisor, not helping your path to completion. 

While you can ask for a different supervisor, that would set you back, possibly for years and not necessarily leaving you in a better situation, depending on the local culture generally. 

You have been given a steep hill to climb - two papers, etc. Start climbing. Do what you can. That is, in fact, all you can do anyway, but give it a good effort. Everything you do for that will get you closer to completion and will help build a good record of accomplishment for a future position. 

I would, myself, try to work on the two papers in tandem. Getting a rough outline of both as quickly as possible and then filling in the details as it becomes possible. I assume that the work behind the dissertation contributes to the papers and is done or nearly so. That might make it possible to work on all three items simultaneously. Then, as the deadlines approach you will have made progress and if you need additional time for completion you have an argument for it and additional funding. 

No, it isn't right or fair. But a short term push toward a better future might be better than just fighting it when you have not much chance of winning the fight.