Hey there, it seems like you are in quite a tight situation there. But don't worry, you'll eventually get ahead by that time.

I can't say what you'll do but I surely can suggest you some advice. 250 days is a long time and I'm sure you'll make it out well.

First of all, if you have access to weights, then you can just do all the basic exercises with your extra weights. For example, pushups and pull-ups with weight will surely make you stronger. And if you do it at least 150 days, you'll be a beast in no time.

And secondly, if you got limited access to machines, I suggest you better stick to basic calisthenics workouts. There are tons of different workout for your whole body.

And lastly, for endurance, I'm sure simple jogging or pull-ups will do the work. All of this exercise will require only your height of space. So it'll be easy to manage your space.

If you want, here is a link to my sorry on how you can improve your pull-ups. Also, if interested in calisthenics, here is another story for you to get started. These may help you in any way.