Looks like what was required was less theory and a bit more praxis. I ran a #14 white from the DC buss to the lug on the socket shell tonite and (with the AC main breaker off) was able to power the inverter and my laptop AND 2 DC LEDs, 1 incandescent in the range hood, the range hood fan and the FantasticFan on high spd without an apparent brownout, red
light on the inverter, or loud beep. I removed the tap to a side marker lamp lead in the frig comptmt (attached by wire nut) and spliced the sidemarker lead with a butt connector. This is considerable improvement on the experiment hooking the buss to the shell with an alligator clip lead. I had used the allligator jumper to ground a 12 ga. shotshell reloader in my basement so the gator clips were probably not clean metal. I did have the converter box as far into the aisle as it will come to open the clamp on a box connector to get the lead thru but didn't have enuf slack to examine the problem of tied grounds or frame ground on the AC. If the retrojockeys at Camping World et al weren't so damn stingy with wire (some of this stuff looks like it was installed with a barbed wire stretcher and cranked up to high C) maybe a bit of troubleshooting could be done by simple physical examination but I found it impossible to do so--probably also partially due to my own lack of sophistication about matters
electrical. Again thanks to both Bill and Jon for the patient advice.
jack