For not-super-expensive, you can't go wrong the hobbyist version of Fusion 360. It's a one year subscription, free although it has to be renewed each year. There's tons of features in the free version and at least that many tons of tutorials how to use it. Product Design Online is a YouTube creator with a great series of tutorials, easy to follow, really clear to understand.

With respect to the difficulty with the file, usually turning it into a zip file will let it squeak by the filtes.

I agree with the curious aardvark about doing the work in millimeters. The math is so much easier and the programs behave far better.