i wouldnt disipline anymore then you are doing, too much can cause doggy depression. sounds like your doing a good job so far.

When you leave the house what does he do then, and what do you do when you come back, are you calm or are you just as pleased to see him as he is??

If you dont want to pen him when he gets over the top, try to ignore him for the first couple of mins when you get in, then go to great him. if he gets excited again ignore him until he sits, then fuss him, if he gets up again ignore him, only fuss him when hes sitting. ignore him for a few mins before you leave too. or give him a treat (ours get a largish bone shaped buiscit) before you leave then leave quietly, without making a fuss. this teaches him that you leaving is ok i only mention this as it might be a mild case of seperation anxiety and its best to not let it develop further.

to be honest i think your doing a good job, i know it seems unfair penning him up at the moment but he will learn.