Flange problem--need help

Hi, I'm in the process of redoing my 1/2 bath. I put in a new Ultramax toilet today, but ran into problems. The nuts on the closet bolts never got very tight, and I had some problems with the bowl rocking slightly. I thought that possibly the flange was pulling up instead of the bowl tightening down. I pulled the toilet, and sure enough, the flange was slightly above flush with the floor. It started out about 1/4 " below the tile surface. Also, I noticed that the flange is possibly starting to disconnect from the PVC pipe it is attached to (see picture). The screws holding the flange to the subfloor are not doing their job, since they cannot be screwed in tight.

What do I do in this situation? I'm thinking of calling in a plumber tomorrow to see what he can do, but I want to know beforehand what everyone here thinks. Luckily, I have a basement with only a dropped ceiling below the bathroom, so access to the pvc drain pipes is good.

Here are some pictures, including one of the old wax ring right after I pulled the old toilet. There is some funny looking stuff around the flange underneath it, but the subfloor does not appear damaged. Notice what looks to be mushrooms, in a very dried state! I only pulled the toilet a week ago, so any water damage appears to have been from some time ago. There is not obvious damage the wood surrounding the flange, though.

Well, I had a plumber out today. He told me the flange is in fine shape, and so is the rest of the plumbing. The problem is simply that the screws holding the flange to the subfloor need to be taken out and put back in at an angle to "bite" into fresh wood. Alternatively, he said I could screw a couple of pieces of scrap 2 x 4 wood to the bottom of the subfloor, then screw in some longer screws. He also suggested I could strap the 3" waste line to the joist in the basement.

Perhaps those mushrooms you have growing under your toilet can be sliced and used into tonight's spagetti dinner.