If you know the strength at any point in the run, then only the length of cable after the measurement point is important. Overall it's probably a pretty minimal point in most homes though I guess if your cable is routed through multiple floors or in a roundabout way it might make a difference...
Sounds pretty close to the idea. Again measuring the actual incoming voltage seems to be the kicker. The best information I have says the individual TV's strength should be somewhere between 0 and +10 dBmV though you may get a decent signals from -10 to +15. Too little signal and it gets...
Best site for overall information on amps and splitters: http://www.cabletvamps.com/education...Cable% 20Amp? Actually the http://www.cabletvamps.com/index.htm site itself is a wealth of information about CATV, splitters, amps, etc. Overall I would be suspicious about the mutiple...