Do you have a place you can work with your horse inside. Maybe a dry stall or barn isle?
Atleast until the ground dries out.
Personally I would take away the grain for now if he has 24 hour access to hay. How does he look as far as weight? I know one of my horses is on the heavy side from hay and grass.
I would work your horse with backing out of your space. He dosent need to be in your space unless you invite it. Put him on a lead and stand out in front of him. A foot back from his nose will be good. I ask for a back and wiggle my lead from side to side as snake.
If he dosent budge then I would have a crop ready to gently tap his chest asking for a back. If he dosent back tap harder. Only tap as hard as he makes you until he backs. Even if its one foot back stop and praise. Ask for 2 steps and so forth while praising for each effort. Dont expect to much right away. Backing is not a natural step for horses and getting them to do it readily is a respect thing. You will have to astablish yourself as leadmare over him.

Work on leading him on your side. If he pushes in to close use the crop to drive him over. Now only using as much force as he makes you until he moves over. Start with baby steps only tapping lightly giving him time to react. If he dosent then tap harder till he moves over out of your space. Takes time and patience, He will learn as will you.
Now the biting, I call even nipping biting, is NEVER acceptable and the horse will know immediatley that he dosent want to do that again. Its his way of taking charge and showing you he is boss. NEVER! I scream and knock the nose mighty hard for a few seconds worth and then go on as usual.

Even a horse with lots of unused energy needs to know his place and no excuses for bad behavior. My horses dont get used alot in the winter and have more standing time but are never allowed bad behavior.

There is so much you can do in the stall to keep his mind thinking until you can ride safely.

I would look for someone near you that has a good head on their shoulders with handling horses to help you.

Check into a 4-H leader in your area and maybe get involved with them as a helper. You will find horse people that would be happy to help you with advise or some hands on.

Good luck and stay safe.