Thanks trasla
I've made a new backup. I always try to have as little as possible lying at the online exchanges, as they may get robbed or go bust any moment, so I'm not sending everything to an online service. Moving funds to a new wallet, which I don't know also makes me feel a bit unsafe, so I bought a cheap tablet and installed Mycelium on that, backed up it's master seed and moved everything here.
It would have been nice if Mycelium-wallet supported the "compromised master seed"-scenario and could have generate a new master seed on the same device.