It looks to me like just applying salicylic acid was a mistake! I'm not a doctor but I have had experience with plantar warts and was recently able to get rid of a deep, painful one in 3 weeks and it has never returned to date. See, a plantar wart grows inward so you have to push it out for the acid to be effective. Otherwise you'll just burn the skin around it and the surface of the wart but not kill it.
I used the duct tape method for a couple weeks, used epsom salt soaks and then used salicylic acid pads which create pressure around the wart and force it out when you walk. **My wart was in the same exact spot as yours.
I also created a 3 time post (it was supposed to be a 1 time post lol) blog that documented the process. It goes into more detail and has before and after photos. Check it out if you'd like. I'm confidant a process like this would work for your situation. Although, again, I'm not a doc.