You're right about how he'd be holding the lance, when I originally wrote that portion I was operating under the assumption that Lith was spear-shaped, which isn't the case.
For the size, it would only be slightly larger than a standard lance, unless you had the petals standing on end and sticking straight out, but then there would be gaps through which the electricity could pass without striking it (assuming that the petals face the tip of the lance).
With regards to Arty's electricity, he can very definitely control it. If he couldn't, no bolt would ever make it ten meters, much less a hundred. If he couldn't control it, it would ground itself the instant it left his hand and just plow right into the ground or the nearest grounded object. This isn't the first time he's arced a bolt around something, and nobody had an issue the first time it happened.
As for charging, the biggest drain with the sword is its creation, when he's expending a bunch of power to get it made. Once its made, there's very little maintenance because it's a fairly closed system. The sword was also made in a post prior to the one where he began charging his bolt, so there isn't a noticeably substantial effect on the power of either. If he'd made the sword while he was charging the bolt, there would definitely be a drain on the power of the bolt, just as there would be if he were to use any other powerful active ability (like creating gusts of wind).
Most of the wording in the description of that previous bolt was artistic fluff and hyperbole. All it was meant to do was get across the fact that the guy it was hitting wasn't going to get out of it alive, because he simply didn't have the durability required to withstand 2000 degree heat and all the electrical power that was generating it. He also had no means of launching a viable defense.
In closing, I'm honestly torn right now. On the one hand, the bolt was specifically fired in an upward arc then coming down toward your character's head, and your character's lance was specifically held in between the two combatants, which would put it out of position to block the lightning bolt without substantial movement. Getting hit by an undefended bolt would very likely kill your character, even with his superhuman physical stats, and that's what would be most likely to happen with all variables taken into consideration. On the other hand, I don't want to be a dick about this and force you to kill your character, and while the lance could absorb enough energy to make the attack survivable, it wouldn't negate it completely like you say it does in the original post. Either way, you would need to take damage, and while the logical, no-nonsense part of me wants to play this out in the most realistic way possible (your character dying), the good sportsman part of me wants to cut you a break and let the facts slide just a bit this time. So I leave the choice up to you. Realism and character death or sportsmanship and we keep fighting. Either way, I'm not going to hold anything against you (as long as you don't completely ignore the damage).
Though Drall has a point about the Mach 1 hit. That would hurt like hell, high gravity and glancing blow or not. You also would have likely been flung a couple dozen feet through the air and not been able to grab the dagger.