Outer Blade Edge Foot Pain

I’ve been walking just shy of 3 miles a day 4+ days a week. I had some foot pain at first that I narrowed down to not knowing you are supposed to replace your shoes every so many miles. I bought new Asics, still had some mild pain, bought compression ankle socks, and was pretty good from there on. Then I went on a week long vacation where I was walking mostly in flip flops, not for exercise.

Ever since that vacation, when I do my normal walk, the outer blade edge of my foot hurts so badly by the end that I am fighting back tears for ~10 mins. The pain seems to increase on inclines; the last ~1/4 mile of my walk is a gradual incline up to my house. There are several other inclines along my route and my feet will hurt on those, after those, but the pain will start to go away on the more flat sections.

I *think* I might have a high arch and need insoles but figured I ask this community before buying another product that may or may not help.

Also, I have a damn hard time getting my heart rate up and maintaining it. My watch uses PAI-which is related to heart rate-I used to average 14+ points per walk, after vacation I’m lucky to get 9. I assume this is just my endurance getting better? Is there a way I can make my walk more challenging? Walking further isn’t an option until the foot pain is under control; I hate jogging/running; I can’t tolerate walking in a sweatshirt in Florida heat. I think I’m SOL on increasing difficulty?