1) Since you already tried new batteries (which would've been my first suggestion), I would check all wires and contacts (even on and in the battery pack) for any issues. If that looks okay, you'll probably have to replace the board. I think it has something to do with the contacts between the batteries and the battery pack....
2) Definitely possible, especially if it's necessary to replace the board.
3) US even fixes sabers that are out of warranty. However, you'll not only have to pay for shipping (both ways), but also for the parts and labour. Exact costs can be obtained from the customer service - contact Marlena at
marlena@ultrasabers.com, she's responsible for these cases right now.
4) Also a good idea - we're looking forward to your project if you decide to go that way