Is the area swollen? Can you still flex your foot OK?
I'd start with the most likely problem before thinking it might be a stress fracture. It sounds like a common running problem - inflammation of one of the tendons running along the top of your foot, usually the largest of these (extensor tendonitis).
The main cause of this is lacing your shoes up too tightly! So try loosening them and see how you get on. Also can be caused by suddenly increasing your training, especially uphill work. Cut hills out for the time being and ice your foot regularly.
Pain might linger for a few weeks but should clear up.
Wow, far more here than I could ever suggest about training.
The 'wall' which can happen in a hard-paced marathon from about 18 miles onwards is a caused by a triple whammy of exhaustion, dehydration, and hypoglycaemia.
You've got to remember you have only done two marathons, and no doubt in hot conditions. There is a lot to learn about yourself during the first six or so marathons you do. Although you can train yourself not to 'wall' - in effect pushing the 'wall' beyond the 26-mile point (excellent suggestions above) - there are other things to consider. For instance, are you drinking enough and taking on fuel enough?
The Rotor looks a bit warm to run in? I notice there's a gilet version 'Finch Vest' which looks interesting.
I have to admit though I've never been cold whilst running with relatively low-tech gear. I'm obviously not entering the right sorts of events!
I'd like to have a go at the Fellsman at some point.
An important thing is to have a windproof beanie. I've just got a Nike one and like the feeling of invincibility when you go out in bad conditions with that on.
I also have OMM Kamleika top and bottom which are excellent.
One item I can't recommend is OMM Cypher jacket. In the hood/shoulder area it went dark on the inside and bubbly on the outside meaning water now comes through the fabric in those areas. Not sure what is going on there - none of the rest of the jacket is affected and I washed it properly. It's also too short at the front and the 'welded' pockets soon came unwelded (and I'm not sure how to re-weld them). Waste of £215, that was.