The door looks good and solid but it does have a lot of paint layers (bronze, green, bronze, blue). Also, it has bondo on there already. You might want to get it blasted and strip everything off the door. Did you wipe done the door with grease and wax remover before sanding? If not, do it now. W & G will not come off with sanding. You will have issues with your paint later if you don't get rid of W & G today..

I had a lot of thick layers of paint to strip down on my trunk. Took forever to sand and I still could not get it completely stripped. I finally got it blasted. Some spray filler was required and that was easy to fix. Now I don't have all that old paint on the trunk to worry about.

If you have no rust then I would leave the inside bottom. Trouble is, if you can't get it clean, then your risk trapping moisture and then your door will rust. You generally don't want to put that type of rust treatment on painted surfaces. From your pics, it does not look like you have any rust issues.

I agree with your procedures for preping sealing, filler etc. you noted above.

Good luck!