...haven't read thru all of this, but have been in the spot... "I wish U loved me, like U love that Fing car."
Bottom line, there are far worst things that I could love to do, which can be damaging to the relationship. I spend less on my car that she would shoes, make-up, or whatever other hobby tickled her fancy. I buy, sell, trade and give away stuff to other ppl in the same Supra community.
Since my MKIII was alread down, when I met my GF, it has not been an issue. She has followed the forums and when the time came, I got her an MKIV (which she seems to love more than me ;-)
The only time when an utimatum needs to be given, is when something is truly damaging a relationship (drugs, infidelity, gambling, etc). With the car, U know he's at home, in the garage, etc, etc..... where he belongs. Understand that you should just be supportive and not make this a wedge between U.
It takes a LOOOOOOOOOOOOOOOOOONNNNNNNNNGGGGGG time for withdrawal from a Supra. it is not a simple 12-step process and some ppl stay addicted ALL their lives ;-)