The ones on my '18 were also very tight when I removed them.

I'd try using an air impact gun before I'd use a large ratchet or breaker bar.

Just a tad each way (in and out) at first then gradually a tad more once it "breaks" loose.

Once you get the bolt removed, wire brush the threads on the bolt and go easy on the Loctite when re-installing.

 

Remember you are dealing with a type of plastic that has a corrosive action with metal. A bit of heat goes a long way.

 

HD uses some kind of white thread loctite on those bolts. Applying heat to the bolt will work

 

I went with Tall Boys Cycle floorboard extenders because they not only moved them out but lowered them. At 6'2" it made a big difference in my riding comfort.

https://www.tallboyscycles.com/

 

Did you have to do anything with the parking brake to get these to fit? I would like to put them on a Freewheeler....

 

I installed these on my 12 FLH. I have no idea about your parking brake. You would have to check out the Tall Boys web site.
https://www.tallboyscycles.com/