If a gentle tug on the cambolt with wrench won't move it, it's seized from oil starvation. Pull a cam bearing cap off and you'll probably see some wear patterns from lack of oil. Not to worry though.
The blockage occurs in the head gasket in the cross over between the block oil hole and the number two cylinder head bolt hole, which feeds the gallery in the head. At least that's where the plug was in all of the B21's and B23's I repaired over the years. The B230 had a larger crossover, and didn't seem to experience this problem as much.
The head has to come off to remove the plug. Hone the cam bearing bores a bit with a wheel cylinder hone, and polish the bearing journals on the cam.
If you think the head doesn't have to come off, and that the blockages are elsewhere, then remove the t-belt and spin the intermediate shaft with speed handle or a drill, and watch for oil flow. There probably won't be any in the head.