You’re about 4 months post stroke now aren’t you?
Going back to your first post, you were already ‘ walking 3 miles today over a day.’
So how exercise are getting over all now?
I do a minimum of 1hr a day between the gym and a few fitness classes; max would be about 3 hours but that’s usually with a coffee break and chin wag with fellow gym buddies between sessions. It’s as much for the social aspects as it is for the fitness 
But, how much is too much is, very much, down to the individual when it comes stroke survivors as it all depends on their current levels of abilities. That’s why everyone is suggesting referring to your local gp’s physio if you have one. I can also self refer to my surgery’s physio and I have in the past just for consultation, needing advice similar to yours and few tips. Sometimes it can be a lot quicker that trying to see your gp 
The general rule of thumb is an hour a day of physical exercise for most people. How much rest depends on age, level of fitness and health. I tend to give myself an hour rest after a long 2hr session. If I only do an hour I’m usually ok to crack on with whatever else I want as long as it’s nothing too strenuous.
But it also depends on the type of exercise you do. If walking for an hour or two, I probably rest for half and hour afterwards with a nice cup of tea. If I went for a 4 mile walk, I’d even stop for a break half way through then put my feet up for an hour when I got home. But I never nap during the day either as I have a hard enough time getting off to sleep as it is since the stroke…despite all the exercise I get 
As to speed, for me it’s about what my brain will allow. I very much feel my brain is in control of that, it has it’s set speeds for certain things and won’t allow me to break it. Walk speeds are not a problem, but my speeds for working out at the gym are kept in check by my brain. If I try to speed up, within seconds I’m right back to slow and steady again 
My brain did catch me out one day when I did a short sprint in a circuit training session at the gym. If was so taken by surprise I nearly tripped over my own feet 
But it’s not as though I’m looking to break any speed records any time soon anyway 
My brain has its generous days…and not so generous other days 
I think my brain needs her own unique name to go with her very own unique identity 
Anyway, don’t know if any of that will help you or not but I wish all the best and good luck.
Lorraine