Have you tried individual toe socks? - Injijni's seem to be the answer- along with: the correct size of shoe, proper lacing technique to stop the foot slipping forward in the shoe, and trimming/ filing the nails down - try looking at "fixing your feet" ( it a whole bookabout feet!) for lots of info.
As a 4 hour marathoner myself- a 3 hour long slow run will be a good bit under 20 miles, if run at an appropriately slow pace. This will make you feel a bit short on mileage. Equally, a 20 miler is going to take sufficiently long that it will wreck the subsequent week's trainig. I tend to go up to about 3and a half hour, but no further than that.
I've done quite a number of marathons, and I would say that it isn't necessary to do the much talked about 5x20 milers to get round in 4 hours, and infact, 5x20 milers would be ahuge problem in a 12 week plan. For my marathons, I do a few 16-18 milers, and sometimes don't get to 20 miles, although since taking up ultra running, and doing a few LSR's of 4.5 hours, my endurance is improving, but I can't do much the following week, so no speed work gets done, and I get slower and slower!
"Anterior knee pain"- -ie pain around the knee cap, is very common in runners who are increasong mileage. It is not usually serious. See a sports physio, I don't think it is likely to be the start of arthritis. Be careful if you see your GP about it- they often tell you stop running when that is not always necessary.
As you get older you will naturally lose muscle mass- so having plenty now is a good thing!- It probably means that you will move up the age group gradings as you keep going. Also, lots of mucle means your basal metabolic rate is high, so it is easier to keep the weight down without eating like a bird.
Too much speedwork , and too little "easy " running in your week might be the problem as far as the lack of progression goes. 80% easy, 20% hard, is what I've heard.
Parkrun thin morning for me- 24:12- not a PB, but a best age- grading for me, as it's 2 years since I set the PB, which as only 8 seconds faster, and being an old wifey, I'm supposed tp be slowing down to zimmer- pace.
Marathon is next sunday for me, so sitting on the sofa watching the olympic marathon is tomorrow's plan.
Well done on a decent parkrun post- ultra, Millsy, but watch you don't damage yourself going back to fast stuff this early.
Well done on all the sup fast running, folks, talk of sub-3 marathons like they are run of the mill always stuns me. My parkrun time apparently predicts a 3:55 marathon, but I don't expect that next week- it would be PB for me!- my old PB of 3:56 was a few years ago, and I don't really expect to get near 4hrs these days.