Hi BoyTwinsMum.
What fuzzywuzzy said, sorry.
What your son revealed was a bit of unvarnished truth, imho. Please, do not ignore it.
Emotionally disconnect from her totally...do not expect anything from her and do not depend on her for anything. If you are caught in circumstances where you must speak to her: polite civility, say nothing of a personal nature, say nothing negative in her presence. Otherwise, stop communicating with her, stop reading and responding to texts and emails; if she phones hand it straight to dh (or get caller ID and don't pick up/insist dh get it). Any contact goes through your dh, he is the ambassador to his family of origin.
Fil...is trying to erase it with manipulative statements on how 'you should take it'. He does not have the full picture, though, assuming mil would not let him screen the antagonizing texts before she sends them to you. His input is designed to make you doubt yourself, doubt your instincts.
I'd say pish posh to him, he can think what he likes.
Your dh may be in a difficult position, but, from reading this board for so long, his circumstances will require a serious decision: who comes first-you or his mother? Yes, ulitmately, it does come down to that. His mother is an adult and will choose however much (honestly or dishonestly) she will be upset or angry or devastated or shocked or ...on and on. You can not influence her feelings. Your dh can not influence her feelings. She has him believing otherwise and enjoys copious amounts of control over him because of it. He is walking on eggshells.