I usually build Will of the Ancients > Ionian Boots > Zhonya's > Deathcap > Void > 6th situational item (Rylai's/Spirit Visage/etc) I choose Ionian Boots over Sorcerer's mainly because I want Vlad's cooldown on E and Q to be super low. His big combo that I use is R > E > Q > W > E > Q, so after using W, your E and Q are already up again to use to secure the kill. As said by sarcasm_is_love, if there is quite a bit of fighting early game, I would rush Zhonya's and sit on Revolver until later.

I pretty much play it safe with Vlad until I get revolver and at least lvl6. During laning, just concentrate on last hitting minions with AA. If enemy top laner decides to come too close, I immediately Q > E (or E>Q if you're sure they're in range) them provided my health is over 60-75% to harass them further away and then run back behind my minions. If enemy decides to attack you, pool towards your turret (add Q/E before if you are healthy enough). To stay in lane longer, heal yourself by Q-ing minions while last hitting them, but stay away from enemy top if they're aggressive and do more damage than you. If enemy top laner is being dumb and stays in lane even after you ate away at his health with harasses till its low, then I usually go ahead and hit him with Q > E > W for a kill.

I don't worry about stacking E much during low levels. Takes too much HP. Once you get your items, you can start being a little more aggressive and stacking E. You probably know this already, but make sure you aren't using W first, especially at max health, because it eats 20% of current health. I use W as a gap closer after the first Q > E because of the slow, and then pop another Q > E. Your pool is also really useful as a device for a tower dive, or dodging ults.

As for Vlad's ult, if possible, I would try to drop it on at least 2 people. It's apparently possible to hit the entire enemy team if they're really clumped (say in front of dragon/baron pit). Only time I would use ult on one person is if they are a high priority target and I can burst them or if you know you probably won't be fighting for a bit longer. Cooldown on ult is kind of long though, so I prioritize using it during team fights since anyone infected by Hemoplague takes an extra 12% damage for 5 seconds from ALL sources, aka your teammates.

Hope this helps! Sorry if you knew some of this stuff already, I attempted to address your points specifically but found myself rambling.