There is no database limit, it's just about the source of the data. We already get dozens of FIR from the AIS website and it didn't seem wise to burden them still further for FIR that very few users need. However, if there is enough interest I am happy to add them.
As for the source of Notams that you mention, I have no idea how reliable that source is. The trouble with that one is that it doesn't include the Q-line, the mechanism by which we determine the area of influence for any Notam. As such, that particular source isn't much use to me.