Seeking a little advice. Hopefully one of you can help. Sorry this is a bit long.

I am a new Betta owner and still learning.
A little background:
Bubbles is in a 2.5 gallon tank. While I have a heater, it has been warm here this past 2 weeks and Bubbles' tank is maintaining a temp between 76-78. Sometimes goes up to 80 but it's rare. It's filtered and has a good PH.
Last week I left town for 6 days. While I am fully aware I made some mistakes, I have learned from them. Before I left I did a 50% water change in his tank. About 2 days before that, I did a 100% water change. While gone, I left the filter running and put one of those auto-feeding cubes in his tank. (that is a mistake IMO that I learned from.) It was warm while I was gone, so I don't think his tank's temp changed much.
When I came home, Bubbles was NOT doing well. He was floating on his side. He'd get himself upright and try to swim, but would just end up floating back up to the top and then back on his side. I thought FOR SURE he was a goner and honestly prepared myself for him not being alive the following morning.
I did a water change feeling there was probably too much ammonia in the tank from the auto feeder. I also put some Betta Revive in the tank when I placed him back in. I also put a little bit of aquarium salt. When I woke up the next morning, he was back to swimming normally around the tank. He still had a little bit of a tilt as he swam, but that went away through out the day.
It's been 3 days since this has happened. He seems MUCH better. He built his biggest bubble nest the night before last. Just seems happy as a clam. :)
I do think he has some minor fin rot, which I am asking your opinion on. I have been treating it as fin rot with Mardel Maracyn. The other thing is he has a small white spot on him. Looking close, it looks like a scale that isn't laying flat but I am not 100% sure. I'm wondering what you all think it is. Sorry it's hard to see in the pictures. It's a hard picture to take. :(
I wish I had better pictures. He's great about posing but then quickly moves once I click the button. It's like he knows I am taking pictures!
Tail Rot?
Spot: