Itch have a 1GB restriction on uploads now.
Can I ask you to desribe your .exe problem a bit clearer? Is it related to the source of the downlad - so mega?
Well from what I understand about the itch app, if you don't install through the app, then you need to run the EXE file from wherever you choose to download it. The app only shows the original option to install, and then it goes through the whole 'hosted by a third party' spiel, but you can't launch it from the app itself. Unless there's a workaround, I don't think the app is advanced enough to specify launching a game from an outside source (your HDD).
As for the Mega thing. It has a habit of blocking downloads after so many times in a time frame. The problem, is that sometimes it decides to do this even if you haven't downloaded anything. Which means ppl are having to either wait for an extended time, or sometimes aren't able to download the game at all.
Granted different options work for different ppl, but if you can add a couple other download sites, then there's a good chance that more ppl can actually get it.