I am by no means a "superman", 6'3" and 16 stone. No training for the SWCP but decided to walk myself into fitness. I didn't have any rest days on the SWCP and didn't have a problem with "stress fractures", I carried minimal, although not lightweight, camping equipment, (tent, sleeping bag and sleeping mat) no cooking facilities. Decided that if I couldn't get food for one night it wouldn't kill me but make me get up earlier to get breakfast somewhere. The point I am making is that why should you have got a stress fracture when I didn't walking for 5 weeks. A reason may be that when I tried to walk Lejog in one go a couple of years ago I had to give up after about 3 days as I hurt my hip, I think it was from walking too fast, quite a lot on roads and walking too far each day trying to push myself. So suggest that you need to take it easy at the start in both mileage and speed. I wouldn't book ahead but carry minimal camping stuff as I did on the SWCP so that you can walk or stop as you go. My reserve food in case I had to miss an evening meal was a packet of ginger biscuits, but as you are aware I found B&B every night! Not sure that booking B&Bs so far ahead is a good idea as that, like me, may make you push yourself too much.
Instead of walking the SWCP at the start why not go through the centre of Cornwall?
Lulworth to Swanage I recorded as 4,403'. I use one walking pole, it helps my old knees get over stiles. Hankies - 2 is enough for anyone walking all of Lejog, one for the day and one for the evening!
I never did walk Lejog in one session which is a disappointment but I have now completed it having joined up the bits between the National Trails i.e. SWCP, Offa's Dyke, Pennine Way, West Highland Way and the Great Glenn Way.
Let us know when you are starting and if you are able update us frequently as, if you are OK with it, some of us may like a day or so walking with you if you are close to our home.