Don't let this dishearten you... Getting stuck in a couch is just a bad situation, and if you are still working for his trust something like this can set you back weeks. How are you holding him when you take him out? To earn my blood's trust I had to hold him for 10-20 minutes a day for a couple months. I would stick to sitting on the floor with the snake on your lap, with you making minimal movements. Let the snake decide what it wants to do, hissing is perfectly normal. Can't say it will work, but I wouldn't give up.