I don't know about the REI Halo, but most down sleeping bags (at least the higher end models) have a really good DWR (durable water repellent) finish. You can test this at home with a spray bottle. Spray a section of the outer shell of your sleeping bag with a fine spray. Watch it for about half an hour and see if it soaks in--it shouldn't! If it does soak in, spray the outer shell with a good DWR (Durable Water Repellent) treatment (see next paragraph) and dry the bag in the dryer (low heat).
When it's time to clean your bag, carefully follow
the directions on the Western Mountaineering website. The instructions include how to renew the DWR finish.
Try to get more ventilation into your tent--don't close it up!
Here's a good article on managing condensation in a single wall tent. In addition, be sure the sleeping bag and all insulating clothing stay dry in your pack. Inevitably at some point you will encounter a heavy all-day rain and/or slip and fall during a stream ford. Pack covers will not keep your pack dry under either circumstance. A poncho or Packa won't keep your pack dry either when it's off your back or in case of immersion. Stuff sacks are not waterproof--dump one into the bathtub and see what happens! Either use a waterproof dry bag or a waterproof pack liner (be sure the closure is waterproof). Many use just the pack liner (check it daily for holes) and no stuff sack. I personally prefer to use a dry bag for my sleeping bag and another for my insulating clothing, and ditch the pack liner. Either method will work.
In addition, don't unpack your pack during a rain until you have the tent up, so you have a dry place to unload it. This means keeping the tent at the top of your pack or in a side pocket so you can get at it without exposing the interior of your pack to the rain. Do the reverse when packing up, and have a way to keep your wet tent separated from the dry stuff inside your pack.