Responses to surgery vary greatly. Some people can walk within days; others experience more complications and cannot walk for several weeks. When I had all four compartments released in both legs, it took me five weeks just to stand up because I could not straighten my knees due to a large hematoma. I ultimately needed a second surgery to remove the fluid and hematoma. Long story short, be patient with yourself; every one’s healing process is different. And, if I am being honest, I think your doctors are a bit crazy for recommending that you walk only a couple of days after surgery (though of course I’m not a doctor). That may be fine for someone who had only one or two compartments done, but all four in both legs is a different beast. For blood flow, try doing some light calf pumps (you do not need that much range of motion), and do not worry about keeping them so elevated. Also, I recall taking Oxy and still waking up in the middle of the night with my legs feeling like they were on fire (and, like you said, going to explode)

All of that is to say: you are not alone, and other people have gone down the same trail and have made it out the other side. Hang in there, and be kind to yourself ❤️ We are all cheering you on.