The way your FFP's stand right now, you'd stay with LH because of your 27K Miles on that programm. But be aware LH does require much more miles for an award than UA does. With UA miles you'll get a free trip to the US with 50K miles - on LH you'll need 90K.

Nice trips you are planning, but you had chosen the wrong airlines for any of your programms. If you fares aren't very cheap you should always be allowed to cancel.
Plan your trip to MIA either with UA or LH both will give you miles on M&M for your status. Both do have quite reasonable rates to the US. For your trip to NZ your best bet would be air New Zealand - also brings you status miles on LH or UA.
You flying out of DUS I assume, that you are living in that area, so if you want to, I could help (living in DUS). Send email