ITR Partnership firm

Below are my questions. Please guide me:-
1) I got a partnership firm. So far I have filed NIL returns. 2 returns have been filed NIL. I was not able to operate the firm for some reasons. Is it OK to file NIL return or it can create any sort of problem in the future?
2) Now, I have started getting some work from last few months. But most of my clients deposit money to firm's current account as a cash or from their personal accounts. Is that OK? Will I be able to justify that as an income to the firm?
3) I am the only one working in the firm. The other partner is just my relative as at least 2 partners were required to register as a partnership firm. How much salary I can withdraw from the firm?

Thank you in advance