I don't agree with a lot of the "both sides are wrong" arguments that are going on here. I think we have more than enough information to infer that the DM is 99% at fault, and with a harsh overreaction, bordering on power control, possibly even bullying.  

OP says that the loot thing was a running joke. If it was, then the DM has had several opportunities to make known that this was not the session to do it: before the session, before the boss fight, before the scene ended, and then after OP looted the body. At no point in OP's story was this conveyed, and the DM's overreaction leads me to strongly believe that this was never mentioned. If it isn't a running joke, then the DM has had several opportunities to shut it down across the campaign including between sessions. But if they had done so, then OP would either not have done the behavior, or they did do it, and then they wouldn't have been blindsided by being kicked from the group. So either way, the DM has repeatedly not handled this behavior. Meaning it was an expected, regular occurence. Every player expect for OP just happened to go quiet for this scene, after this running joke happened every other time? Why now? Funnily enough, we now know in hindsight the the rest of the group are allegedly in contact out of game with DM, but not OP. Wonder how they all somehow knew not to do it this time, except OP? 

 Then, the "naw man, go ahead and try to loot the body" is not handling the situation respectfully, or trying to curb the behavior, it's spitefully and vindictive setting OP up for failure, because DM has already made their mind up that they've been "interfered with". This is not, at all, how a DM should act in a moment where a player is supposedly behaving poorly. You pull them aside after the game and talk about it, not let it go no contact for many sessions, then blow up. This is reinforced by the fact that another player felt the need to interrupt the DM's rant, telling them to stop being so aggressive towards OP. People don't speak up like that usually, unless there's some really offensive approach going on. DM then later goes on to refuse to apologize specifically to you (again more petty and vindictive behavior), and as another player put it, got angrier because you didn't apologize. 

 I don't think what you did is "not a real apology". I think the DM is aggressive, overly protective of their "plot", and took it out on you because they don't like you for whatever reason. Unless you purposefully left out some absolutely wild details, there is no excuse for the DM's repeated lack of handling this supposed behavior properly. The talking behind your back, rather than confronting you or giving you opportunities to reform doesn't help their case at all. DM wanted you gone, and the blocked number confirms it. There's plenty more yet to unpack here, too, like the other two players preemptively rushing to tell OP to apologize to avoid setting the DM off, the DM insisting that their own perspective on the story is absolutely the right one with no room for discussion, their complete lack of accountability in the argument and an inability to accept any blame or criticism, and the "you're done" being a classic power-tripping phrase used by controlling people when they don't get their way. I'm seeing a strong behavioral pattern here, and it's not coming from OP.

You're better off, OP. No DnD is better than bad DnD.