I've been researching my own surname for a number of years now and found your discription of its origins the most accurate one that I've so far come across. It's my opinion that the name did indeed come from the Derbyshire and possibly its border area with Staffordshire. My ancestors seem to have originated from around the Ashbourne district.
The Devon and Buckinghamshire links are red herrings as far as I'm concerned. The populus of Wheeldons in the Derbyshire and staffordshire regions far out weighs the number of Wheeldons (and variants) anywhere else in the U.K!
The Old English translation that I have is very similar to your own but with "hwoel" meaning valley as opposed to wheel.
None the less I think that you should be congratulated on a comprehensive discription of the Wheeldon name's origins as many people are so far off the mark it boaders on the ridiculous.