1) All lead cast and swaged bullets of a given caliber and weight use the same load data--you just vary the COL. All jacketed bullet of a given caliber and weight work the same way.
2) Plated bullets used to use ONLY lead data. Now, they are starting to push things and recommending no more than mid-range jacketed data. I "assume" the 1200fps limit still exists for plated.
3) You start at the starting load (I would use the lowest starting load for lead bullets myself as I have a couple of guns that reach max pressure must sooner than the manuals so I always start low) and work up watching for signs of pressure.
4) Needless to say, your buddy's pet load or even mine may be excessive in your gun. YOU have to work up YOUR loads.
5) 231/HP38 is the best choice of those you listed.
6) N320 or N340 might be the cleanest burning. Personally, I put "cleanest burning" so far down on the list of desirable powder traits that I have never even considered it. Every 1000 rounds or so brush off the extractor/breech/feedramp. If your gun can't operate a little dirty, there is something wrong with it