If you will never be close to the gun and kept it at such a low tri count there is no reason for a 2048x2048 map, MAYBE 1024 but could probably sit well with a 512 with no problem.
I thought dpi was just something relevant for printing? If your not gonna print it, it dont matter, all that matters is the resolution(512, 256, 1024 etc).
http://www.thegnomonworkshop.com/store/product/542/ this was announced in the same newsletter and might take care of the texturing - at least for the hard surface stuff. cool dvd anyway
For Bifrost those Compoud Libraries are essential. https://area.autodesk.com/downloads/rebel-pack-040/ https://area.autodesk.com/downloads/mjcg-compounds-132/