I had these exact same issues. I went to the doctor yesterday and he said what causes the choking and vomiting is that your stomach pouch enlarges and flops down around the band (he called it a muffin top). Instead of food going down into your stomach, it goes into the flops of the muffin top and sits there. Then, when you lie down, it comes back up, even if your last meal was 10 hours ago. I had my band completely unfilled and could immediately feel relief when drinking a glass of Water. He said that in most cases, once the band is unfilled, your stomach will fall back through the band and remedy itself. This may be immediate or take some time. In some cases surgery is required to pull the stomach back down.
I had no choking at all last night so I'm hoping my unfill did the trick. I'm going to wait about a month, have an upper GI to see what the pouch looks like and then have a fill, if everything is okay.
If you have choking or feel the band is too tight, SEE YOUR DOCTOR!! Don't wait, it will only make it worse!