I would say German bases are very safe at the moment, however when (IF) BER opens some day, they will probably close SXF and TXL and consolidate them in BER. Question is if they can have all airframes based there (I wouldn't think so because of the size of things), or if they will move some airframes to other locations. - Only time can tell.
Rosters in TXL are rough at the moment due the integration with our new colleagues from Air Berlin, but hopefully this will settle when all is released to fly with each other across the board.
Rosters in SXF are very good, and the stability is generally very good as well.
Part timers have 15-18 days off
pr month - easily, and full timers have 10-12. It all varies on how tactical you are with you leave.