Hi Parallel,
I am by no means well versed in the law but through experience I can say how some scenarios played out for me. I have been in a similar situation whereby my ex used my name and credit score unbeknownst to me to obtain several large short term finance loans and credit cards online when she was preparing to leave with her boyfriend that obviously all fell in my lap after the separation.
First off the Family Court will never take your word for it and given it is illegal to forge a signature with the intent to deceive your best bet is to report it to the Fraud Squad which they will pursue if they think they can build a case. If they do and he is prosecuted and convicted then that is what the Family Court Judge will want to see and of course should hold some weight towards his credibility. My ex was charged and convicted for fraud for using my signature and it definitely made a difference in Family Court.
I'm sorry to say though but my biggest hurdle was getting the Fraud Squad to be interested enough to take on the case because even through my lawyer contacting them they were reluctant as it is common for marriage splits to make accusations against each other misappropriating money and it wasn't until I gave them gold plated evidence of the fraud that they moved forward. It still took several months and my lawyer had to ask for adjournments in Family Court pending the outcome of the criminal investigation which we were fortunately granted.
It is definitely not pretty as you will have to testify and be cross examined and the only reason I did it was to have to $140k high interest debt removed from my name and my credit score restored.
Good luck
