i am answering to your all questions as under here:-
1 yes then it will not be considered no forgery moreover you will be at liberty to file a suit for damages for malacious prosecution and for defamation.
2 yes you can be held guilty and if your wife is also partner inthe firm or the complainant has filed a complaint against both of you the you both can be prosecuted.
3 yes you will be held guilty and also can be punished
4 yes and you may be get the benefit of doubt in that case.