As to defending his supplies, it's not a question of Lee attacking McClellan's supply train I'm thinking of - I'm thinking of Lee wrecking the infrastructure that McClellan would then need to advance over. As of 8-9 November the Army of the Potomac is around Warrenton and Lee is at Culpeper; if Lee wrecks the rail line from Culpeper to Gordonsville (as much as he can while conducting a retreat to Gordonsville) then he's imposed problems on McClellan advancing, or that's the idea anyway.I think McClennan had the troops to defend his supplies, but it's an interesting analysis. Attacking him directly was also a problem. Because when little Mac actually got into a fight, he gave a pretty good account of himself.
Had he been bolder, I think he would have won all the fame and fortune he might have dreamed of.
As to being bolder, on the other hand, the reason McClellan didn't advance on the 10th November is that he'd been fired. Is there a particular period you're thinking of for McClellan lacking boldness?