A lack of proximal leg strength can be a contributing factor for metatarsalgia. But also not enough strength in the foot, too much load from running, bad/old shoes…
I would continue with the leg strengthening. And ad some flexibility and strength training for the foot.
Insoles can be helpful to get rid of the pain, but I would not recommend that as a long-term solution. Unless there is a bigger anatomic problem with the foot.
I also see good results with cortisone injections, but that’s only one of the last steps.
hope that helps?!