Looks like you were running an ultra, not a marathon?! I’m sorry, that you didn’t finish.
As I read this I remember how I felt after my first marathon;-) I gave myself 4 weeks to get back into normal training. I took the first week completely of from running. Only walking and aquajogging and easy (short) cycling. Then only short running sessions every other day to find my rhythm. Always listening to my body. That is also my experience with other athletes.
I ran track and field and then road marathons. Was your race on the trails and a hilly course? I find it’s easier to recover muscle-wise from a trail race. But the overall fatigue stays for longer. That your resting HR is still elevated is a sign that your body is still under stress and busy with recovering. So allow the recovery to happen and don’t stress the body with additional training. I would recommend only short recovery sessions every other day. At least until resting HR is back to normal. Then extend the sessions and see how it feels. I would wait with higher intensity at least for 3-4 weeks after the race. The better you recover now, the easier it will be to progress with training. Do some core. Sleep as much as possible. Eat healthy. Get some sun…
The good thing is, that with more experience you will bounce back much quicker. After some years of marathon running, I felt ready for training after only 1-2 weeks of recovery. …until you joke with your friends: “the older I get, the faster I was”
hope that helps?!
next time you’ll finish! And the better you recover now, the better you will finish;-)