You already have lost: You are on a Mac. Sorry for the bad news, but that's just not gonna work. DivX on Mac is completely different from how it works and behaves on PC and chnaces are you will only end up producing an incompatible file. You really need to have a PC somewhere in there which for all intents and purposes could be a virtualized one running in Parallels on your Mac or a genuine secondary Windows OS using Bootcamp. Then you have plenty of free tools at hand - anything from VirtualDub to ffmpeg and its various UI applications. Your resolution can be attained by setting your MPEG level to 5.1 and thus removing the constraints, for H.264 at least. Not sure about DivX, since I'm not up on all the latest. I believe, though, that this is only possible with their commercial 2k+ and 4k coDecs, not the standard free generic CoDec. Likewise, the availaility of these CoDecs would somewhat determine the data rates. Not sure what specific problems you have, but 1Mbit is still 1000kbit, so you should be able to do the math. The resolution/ spacing of their LED wall doesn't need concern you. Pixels are pixels and for video they are mapped 1:1. If they need to skip any lines or adjust positioning, that's entirely up to their playback software and hardware.
I do have a Windows partition on my Mac, so, can render it in After Effects from there? Or should I just convert the video itself using a converter tool?
I've been trying for what now is, a couple of days to no avail (on Mac, at least).
I used some converters but for some reason their resolution limit is 2000, and my video is 2016.
I'm gonna try to convert it on Windows later. If there's anything any of you guys know that could help me out, please mention it.