I was in a similar situation, although I got more than 3 hours of sleep. I don't think 3 hours of sleep per day is sustainable, you have to find another solution. Any work you do on 3 hours of sleep is probably not great anyway.

I don't know your specific circumstances, but I used low dosage Armodafinil and Melatonin before with with success to get by with little sleep (didn't keep track, but I think at least 6 hours per day). If you are in the US you will need a prescription for Armodafinil, but if you explain your situtation to the doctor it is easy to get one. Armodafinil can be imported cheaply from India. Melatonin is over-the-counter.

Hang in there and good luck!

If you don't stop you might loose any chance of a meaningful life and job for the rest of your life. A burnout is not always possible to recover from.

Stop it, now! You'll always have a second chance but please don't destroy your body.

How are you only getting 3 hours of sleep per day? Genuinely curious. Why does your visa matter so much you're willing to harm yourself in a possibly very serious way? I suggest you take a step back and seriously weigh your options.