Have I become sterile due to masturbation, and will my repentance be accepted after I stole a lot of money from my work and spent it, knowing that I cannot return it?

One must repent to Allah for theft. The condition for repentance from it is to return the stolen item to its owner or to seek their forgiveness. If they do not forgive you, what you stole remains a debt owed by you to them, and you must resolve to return it whenever you are able.