Oh Orm, I really do feel for you - yes it is really much easier to do nowt but as you know only too well, if you make the move and get out there, it makes the world seem so much better.
I only did my 10k last week because of encouragement here, I used to run marathons, then got injured and had to cut back to almost nothing, then Mr T got his incurable/inoperable diagnosis and it was all too easy to hide from stuff but with the support from here and a few hardcore RL friends I'm back again. 6 weeks ago I felt physically ill trying 4-5 miles, now I'm back to 8 - not as fast as I was but I WILL get back and so will you.
NEVER too old but see if you can get guidance from a physio or podiatrist (pref via recommendation so you have confidence in them)
Set yourself realistic targets based on now not how things were. It'll never be as hard to recover your fitness as it was to gain it in the first place but you must have short term goals which are achievable.
Above all, keep trying and stay here! xx