Thanks for writing in,
The Primary cause for all your symptom is Flat foot
which was not treated. Flat foot causes shifting in mechanical axis in foot. So, the normal wear and tear becomes more in the part where stress
is more. This altered mechanics causes plantar fascitis and osteoarthritis
. Flat foot and osteoarthritis can be diagnosed by Xray. Plantar fascitis is basically a clinical diagnosis.
So, if flat foot gets corrected, your symptoms will also decrease. But whatever wear and tear has occurred, can't be reversed back. You should use footwear's with cushioned heel with medial arch support/raise. These footwears should be used both indoor and outdoor. Avoid walking barefooted. For plantar fascitis, you can try stretching your toes by using a piece of cloth. Hot fomentation at the painful site will also help. Losing weight will also decrease the stress and relieve your pain. If pain is more NSAID's SOS can be taken.
Discuss with your doctor and follow his advise.
Wish you a good health.