I feel your frustration. I had one "free day" last weekend, and I wasted a good 4 hours of that day trying to sort out these problems (it became an obsession).
For issue #3 there are two really great "unofficial" workarounds mentioned in the forum. I believe the topics are sticky, so they'll be listed near the top. I was finally able to download using one of those methods, so grabbed all the missing episodes in one shot.
To get past #1, sometimes I got lucky and it let me in. But at one point it just wouldn't for about 10 tries in a row, so I had to launch the game while holding down the space bar. That clears the saved account info from your cache, and lets you enter your username and password again. It's a surefire way of getting in, but I'm wondering if it's also the reason my savegame data got wiped... do this at your own risk. For #2, I just had to keep starting and restarting the game until it finally worked. The moderator is right -- sometimes it just takes a while. Other times it did actually freeze.
Once I got all of that sorted out (and got over the frustration of having my savegame corrupted for the second time), I played through episodes 3 and 4 in one marathon session. The game is so good, it was *almost* worth all of the trouble!