One thing to consider as it's what I had to consider: if you have any kind of arthritis/hand issues, the SDB is very small and 'tight working' conditions (as fredj338 mentioned), so take that into consideration. With my RA, I couldn't get my fingers in the right place to seat bullets, etc...
My answers to your questions:
2. MUCH more enjoyable!
3. The Dillon is GREAT! I too liked the Lee Auto Disk, but the Dillon is amazing compared to it.
4. Squibs and double-charges are USER ERROR. You have to seat the bullet, so look to ensure the powder is correct.
Right now, I'd be more concerned about components than presses... YMMV. Good luck! No need for shame.