I don't understand this idea that Flint's technology requires line of sight. The Federation transporters don't.
Actually, it seems that they do. Even a few kilometers of ordinary rock pose an obstacle for safe transporting, so over-the-horizon beamings should be impossible. Unless transporter beams can somehow curve around obstacles - but that sounds a bit unlikely, as there's indication of their directionality, such as the "collision" between Gary Seven's beam and the Enterprise
Which may relate to the definition of "standard orbit": rather than a freefall ellipse, it may well be a holding pattern over the landing party, guaranteed to keep the team within sight and thus within transporter access.
Then there's the "conservation" argument
And, just like you say, treknology tends to violate most known conservation laws. It should be noted that the transporter is one of the worst offenders in this respect, so Flint using a variant of this technology gives him a carte blanche...
As regards Flint's accumulation of resources, I'd say an important part of that would be a lot of experience in dealing with fellow humans. Supposedly, a millennia-old man would be able to play others like a fiddle, having tried out everything at least once already.
Which actually makes Flint's poor performance in this respect a question to be pondered. Is he finally growing senile and losing his old touch? McCoy's final analysis would appear to support this idea.