Don't worry about a .5 inch dowel not holding his weight - dowels are made out of very hard wood, usually oak, and can hold up to a lot of weight (think about a well-made wooden chair - those are made out of oak or other hard woods and can hold a great deal of weight, several hundred pounds).
If there is nowhere in the house where you husband will allow you to secure a bar, you could try just laying the dowel across two tables or something of that sort as just a temporary support. It might roll so you could just set up large books on each end so that it can't go anywhere. I'm sure you can find some structures in your home that would be suitable to lay a dowel across as a temporary hanging station. And then just lift your baby up to grab the bar and stay with your hands right on his abdomen the catch him when he lets go.
Another option would just be to hold the bar over a bed while he hangs (with a great bunch of soft pillows, in case he falls). When you see his hands start to slip you can gently lower him down, but it's good to have a very soft landing just in case. Although this is kind of difficult with heavy kids (I did this for a while with my son, when he was 2 1/2, and it was hard but it worked!)
It's more convenient to have a bar-hanging station that is permanent but you can make something work with a portable dowel. And, ideally you will eventually have a brachiation ladder that he can hang from, which will be the easiest of all. I have a very small room and didn't think I would be able to have one, but I was able to build an 8-foot long ladder that fits over my queen size bed and therefore takes up virtually no extra room. (see a picture here
http://2.bp.blogspot.com/_wxnBlVg-VSw/SKOuBSkLU0I/AAAAAAAAA0U/NBzaS754Oc8/s1600-h/Rope+swing+08-13+003.jpg)
Hope you find something that works for you and your baby!
Digg
