If you were going paint over after stripping the paper off, then you should have washed the walls down with Sugar soap to get rid of any paste residue and contamination.
The reason you have got a blotchy finish is, as good as you have sanded down the walls, you will still have slight indents from where the old paint have come away from the plaster.
Even after you have rubbed/sanded it down, you would either have to fill these areas, then sand again, and probaly PVA all the filled areas prior to painting as there would be so much filler, that by PVAing it, would stop the filler from blowing or crumbling when you start painting.
The best bet I think is to line the walls.
I will try and upload a pic of a wall very similar to yours, that I filled and PVAed, the one wall was flaking, and no matter how I sanded it, it would flake again, so I PVAed after I sanded, then I did my filling, and there was loads of it, then I PVAed again, as I was hanging lining paper over it, and knew that the filler would blow under the paste, and as good as lining paper is, I know what will show underneath ( I hang enough of it) lol
It would have been quicker to get it skimmed I know, but I had to make decision and couldnt wait for a plasterer, but my efforts have paid off.
Either line the walls or get them skimmed.
Give me a day or two to master the uploading thingy, as I dont normally upload pics, (but just for you I will try)
