I had this, and it lasted just over a year, which appears to be standard, before disappearing completely. It is extremely painful and I do feel your pain. I now own about six pairs of Birkenstocks as a result (they are actually marvellous) and I did buy FitFlops but they didn’t really fit me; sort of weirdly too long in the foot - but if you CAN get them to fit, they are wonderful. Specially made insoles can also be got but they’re very expensive. Apart from a steroid injection which may work, there’s not a lot you can do that you’re not doing already but it is the one thing that seems to have a spontaneous complete resolution after a year or so, unlike most “chronic” illnesses, so you can take hope from that. It was so painful for me for such a long time but it is now completely gone. Hopefully this will happen for you. Personally, I’d say REST your feet as much as possible when you can.