Ok, back up, stop paying for college, get the daughter some help, leave your wife until you know you, and love your other two as much as possible..perhaps they, your kids, are acting that way because they feel that they don't know you, and you don't know them?
Until you are authentic and true to yourself, which will help clear a lot up, no one else knows who you are.
That being said..40k college and tantruming, it's called boundaries, establish some, wife yelling at you, leave you deserve more and believe it or not so does she. The other two, whatever and whoever you truly are needs to respond to them and tell them that it's a bit crazy right now, but Daddy loves them and nothing will ever change that.. If your therapist ain't workin, get another..grow some balls and get going, stop getting kicked...for gods sake, there is joy, happiness,love,excitement, passion, laughter all out there and what you have allowed yourself to become is not the person you are..GET GOING!! And any "other" way out, is an awful legacy for your kids, plus, ITS NOT THE ANSWER!!
I know, bend there dome that, and sometimes relapse....get going, get going get going
I don't have one