PL, don't aim to go too fast - forget where you were before, concentrate on where you are now - you will get fitter, faster and back to "normal" and then even better
.
Take it easy - aim for time on feet rather than distance - building back up gradually ( I did mine in 5/10mins stints). Start each run slowly and build up speed during the run, after a break it's so much easier to set off far too fast, then.........

.
There's nowt wrong with walking either - I know a lot of people turn their noses up, bit it's a great way of getting back into training after injury - I used to do run/walk combo at the beginning as well. Might not be such a bad idea if you've now got orthotics as they will push/pull your body in a different way and might take a bit of getting used to in the early days.
Go for races, but maybe lower your sights (if you were previously aiming for 10ks, go for 5k etc) to start with and give yourself a few weeks to get back into fitness. Add x-training too, if you can.
I was on the bench for about 6 - 8 weeks in the spring with 2 - 2 1/2 st weight gain (medical problem). I did my first race (10k) mid June and really struggled. I picked up training again in July and I'm now up to HM distance. I've lost some of the weight - (unfortunately it won't go off as quickly as it went on
) and am working at losing the rest.
Plenty of us in similar situations to you so
and hope it gets better for you.