Coming back to this:
Oh jeez

I hadn't really looked at your avatar earlier, but the intp I'm on about has a picture of Chris Hansen on one of his profiles. Next question: The significance, if any? lol
No significance. Just thought it was funny. Mainly cuz he's talking to YOU, the members of TypoC. When you look at the avatar, for a moment you're the invader! You're caught and the eyes bulge out of your head. And you say, "uhhh, I was just here to meet a friend." Hahaha.
That and how to not step heavily on spots that would make an INTP recoil.
Well, hopefully I answered the first part already. He needs something of worth, something of long-term value to engage in. If all he's doing is 9-to-5 drivel or just not being productive at all (we do need our down time, that's for sure - time to noodle around with ideas and think about the meaning of life and all that other jazz), then it's easy to start thinking, "Life is meaningless." And that's not a good place to be. Once you give up in your spirit, it goes downhill real quick. But, he can get it back - that zest for life. He has to get back to doing the things he enjoys the most, the things he has natural talents for. Be him. A little social conformity is required sometimes to make things work (you gotta pay bills, you gotta hold down a job to get back on your feet before you can branch out on your own, etc.), but there is definitely a path that can be followed or taken that will get him to a good place where he's doing the things he's good at. But, it won't be handed to him on a silver platter or spoon fed to him. I think a lot of INTP's make that mistake - myself included in my early 20's. I thought just cuz I had good ideas and I could learn quickly, that I was going to be successful in the things I wanted to pursue. It takes a little more than that though. It requires you to keep walking - a consistent, day-in and day-out walk, putting one foot in front of the other. Make progress daily. Do something big each day to get closer to your dreams. Not just little, meaningless stuff like paperwork. Something big, some major step each day. Or even 1 per week. Make progress, move forward. Next thing you know, you'll be walking in it someday. Just takes a little determination and dedication.
Give him a pep talk like this. Use your Fe to encourage and show him that he's talented and it's not over. Sometimes the best place to be is at "level zero" (like he seems to be). That's actually not a bad place. Cuz now he can start rebuilding from the ground up. Building a foundation for the future, refocusing on what he wants to do and wants to become, etc. Sometimes the 2 best things I can hear are: (a) you're acting like a fool, followed by (b) but there's so many things you can do. Don't get bogged down, the world is your oyster sort of thing. Beat him up, but then build him back up with some encouragement! And INTP's are big on being "competent" - maybe point out to him all the ways that you think he is really competent. Dude, you're soooo good at x, and you're really talented at y, you just have to pursue those things and get that pep back in your step and you'll be fine. Don't let those talents go to waste. That doesn't mean you have to put pressure on yourself to be some uber-successful millionaire, but make sure you're tapping into your talents and making use of them in some way. Something to let him know that you see the capabilities he possesses.
The "acting like a fool" thing is not going to hurt his feelings. It's a rude awakening. It's like the really loud alarm clock that goes off after a long night. It wakes you up. Snaps you out of it. He'll respect you for saying it, but it usually won't hurt the INTP's feelings. He can take it and it's probably what he needs to hear. That's much, much better than "awwwww, you're just in a bad spot right now. Everything is going to be OK." <-----------although that type of "cotton candy" can get us in a playful mood too, which is also good
But, about stepping on his toes/making him recoil - as an ENFJ I would say "do not FORCE"; do not push. Just dialogue with him, interact with him, and tell him some of the things I mentioned above. Then it's up to him to move into action. But, I've had extroverts say to me, "You just have to get out and come to this party with me." "Uhhh, no I don't. I don't want to do that." "Yes, that's what you need." Don't go there. Don't force him to do stuff he doesn't want to do. Just because it would be healing to you, doesn't mean it's the answer for him.
I dunno, you kind of have to get tough with INTP's sometimes. Tell 'em what they're doing wrong - deal direct. Shoot straight from the hip. Don't sugarcoat. I'd rather hear, "Look dude, you need to get your stuff together ASAP, stop acting like a clown". You say stuff like that, and you'll have my attention. Then I'll think, "wow, I really must be acting a fool if they said it like that. Let me re-evaluate what I'm doing here."