30 years! Wow. I'm so sorry this is happening. I'm sorry about your MIL's loyalty- have you talked to her?
Have you taken any steps to protect yourself (financially/legally)? Those vehicles should be partly yours after 30 years of marriage, right?
I've hidden every shred of paperwork to prevent my WS from coming in when I'm not home and taking stuff. I literally emptied the filing cabinet and stashed everything at another location- if he wants something, he can ask for it, and I can take copies first. Like your H, I suspect that mine may be doing hinky things with finances.
Me-29 H- 28 Together for 6.5 years 2 kids, ages 9 and 5 D-Day: July 15, 2010.