Is it possible to compress/degrade a .tga image to a specific file size/range? I read about RLE compression, and from what else I've read, this seems to be the only way to compress it. Other than that I'm at a loss/ My searches have so far turned up nothing useful.
RLE compression option is either On or Off, you can't control how good it works.
Although if you need to get best results you could prepare your image and reduce color count in it (e.g. by converting it to paletted image and back to 32bit). When there are fewer different colors in image, it allows compression to work better (by finding identical patterns in previous compressed data). Fewer colors -> more repeating patterns -> better compression -> smaller image size in result.
Another option to make compressed image size smaller - delete RGB data in areas that are completely transparent. That will allow compression to be more effective as well.