It looks like we've successfully found a Nachmieter to take over our lease. Now I have to ask, are there any obligations on my part if the Nachmieter signs a new contract with the landlord and then turns out to be a deadbeat?

Not that I think this guy is, but I want to be certain I have no further obligations once we have moved out, and that I will get my deposit back after the Nebenkosten is calculated for the year, etc. So, if the new tenant breaks his lease, turns out to be insolvent, or anything else, once we've transfered the lease, we're off the hook regardless, right?

Thanks in advance.

I would think so, so once you move out and he moves in there shouldn't be any comeback on you. As you say, it's a new contract between the tenant and landlord and nothing to do with you. If the landlord is happy then it should be fine.