Patience, patience, patience and some Feliway sounds like a good way to go.

I adopted an older cat last year (she was 10) who had some odd behaviors as well. She didn't like people touching her back and didn't like being held. She actually lived for the first few weeks at my house IN the easy chair -- in the part where the guts of the chair are. She squeezed in there and would stay in there all day. I know she came out for food/bathroom, because the litter box was dirty and the food would disappear. After almost three weeks, one day I came home from work and she was out from the chair and sitting on the floor.

Another week goes by, she's at the front door waiting for me to come home.

It took a couple of months before she was comfortable enough and knew me and the house enough to not hide and begin to interact with me.

I have had Minnie now for 1.5 years -- she loooooooooves to have back rubbies, tummy tubbies too! Who would have thought.

As for closed doors - their curiosity kicks in. They just need to know

Hope you continue to make progress. Slowly but surely, your furry friend will come out from underneath the bed -- you just need to entice him a little bit with a treat or a toy. He may not respond at first, but over time I'm sure he will. I wouldn't force him from underneath the bed. I would leave little treats/toys on the floor so he has to come out to see them.