aye...rockbox should solve all those issues. the iriver firmware basically sucks for recording - but with rockbox they become lean mean taping machines.
1) yes, you'll be able to control recording levels.
2) it should solve the skipping - that sounds like a known iriver f/w issue
3) you can keep recording until you fill your hdd - in lossless wav too...no mp3s.
4) not sure about the static - could be that the mds supply more power to the mics.