This is interesting because I've seen this kind of behavior. When most people looking at the purchases would conclude that they were irrational, you can say they were at least impulsive and probably compulsive. You'd have to tell me whether you consider someone entirely responsible for their compulsive behaviors.
I had an employee who was homeless, yet constantly -- and I mean daily -- picked up junk from the gutter that people were throwing out ('perfectly good...just needs a little fixing...can you believe they were throwing it away?!'). It was a compulsive behavior to the point that he would bring back furniture in the company vehicle -- mind you, he was homeless! No place to put them! We just figured it was a sort of unconscious reflection of his desire to have a normal life, a place where he could (never mind that he probably never would) store and sort and work on these things.
But in all this time he never actually moved forward to resolve his lack of shelter. It was like some kind of anxious displacement of his paralysis on that front, that he would keep doing these things that seemed so out of touch with reality.
Like D's desire to pay his own debt and your schooling, it isn't just a lack of realistic planning. It's a reflection of the distress, confusion, and shame he probably feels for having failed at something that is very basic to many men: providing for our families, managing the finances, and so on.
I would imagine he has many irrational beliefs about this situation that are causing him to be upset. And it doesn't help, sometimes, when the spouse is taking charge and bringing order out of the chaos. It forces him to face those irrational beliefs, while up until now he's been able to submerge them, even placate the distress somewhat by continuing the behavior. See, if he can just get some more of this, or organize that, he can get caught up and make something of all that stuff. I imagine if you had a big garage sale he'd probably suffer considerable emotional anguish. So this may be something you'll want to approach rather gingerly, meanwhile making sound financial plans and goals of your own.
So much for my armchair analysis! Take care, and keep your expectations realistic!