Vclaw
4
Yes, as MikeN says, individual properties are not usually mapped in OSM. Though if there’s a fence or a wall you can map that, plus any building outlines etc.
For addresses, interpolation is a way of mapping lots of numbers quickly. But its not necessarily very accurate, eg if the spacing between houses varies, or if some numbers are missed out. I think its best, to map individual house numbers as nodes, or where possibl, tag it on the building outlines.
For other things to do, it is worth checking some of the quality assurance tools: http://wiki.openstreetmap.org/wiki/Quality_Assurance
Specifically, have a look at Keepright and OSM Inspector. These can highlight a variety of possible errors. You may be able to fix some of these using aerial imagery / local knowledge etc, though some errors may need surveyed to check what is actually there.
You can also check OpenStreetBugs and MapDust to see if there is any problems reported by others.