talk to him directly freewill... i understand why you are mad. i would never and could never share. i understand some people do and bless them they are stronger than i.
i dont know if it's applicable, but my mom redirects her anger... transfers it i guess... she cant stand my SIL ( no one can, she's a ***** who abused the kids) but she cannot seem to direct the anger to where it belongs... she's mad at my bro for taking the horrid cow back... but she cannot seem to tell him... so the anger leaks out everywhere.
redirecting anger at T is not a bad thing, if you tell him. He can help you work through that... but he has to own the parts of it that are legitimately his.. some T's aren't good at that part. He's made a bad call not to foresee some of this... oversight at best.
it cannot be worked out any other way than through it... and that may also mean telling your son that he has also made you very angry. Afterall, the anger is with the two people you care about... the super-***** doesn't deserve that level of feeling, she's a nothing.
sending warm fuzzies
ps... i am so deeply sorry about your dog

i am highly triggered by such things and could not respond to your post. Blessings sweetie.