Interesting that the memory usage under "manage my content" page shows used 3GB, unused .63GB, my guess is this has something to do with maps not installing, there is no space.
The process happens in two steps. The first is that the content is retrieved from the TT server and stored on your PC. The second step is that the content is copied from your PC to your device. It sounds like the download has been going OK (but slow). It's the process of moving that content to your 1505 where the previous content is overwritten by the new content. There's no reason why there should be a bunch of empty space on your 1505, so don't fret about that.
Another issue is that they are very hard to understand, there English is very broken.
As I understand it, they've moved their support to Mexico. I had occasion to talk to someone down there the other day, and was actually pleased with both the command of English and the lack of strong accent. I did have her repeat a couple of things using phonetics to be sure (e.g., TOM for T, MARY for M, etc.), but that would have been true in most cases. Guess it's all a matter of who you get on the other end.
What I find interesting is that they are suggesting you pick up an XXL540 or similar as a replacement. Truth to tell, an XXL540TM is a fine little unit, and we can actually keep you out of trouble with one of those since the file system is accessible.