How do I eliminate save option after signature and also prevent signature if field form is empty?

Hello:

Two part question:

1) What javascript could I use to get rid of a save option after placing one's signature? I already have a save button at the very end of the from and I don't want to annoy those using my form to have to save every time they sign;

2) Also, what javascript could I use to warn users that they must complete all form fields before signing should a field be missing content?

All help is appreciated.