I apologise if these have already been discussed bu i have just a couple of questions:

What is the maximum level that vampiric seduction can reach? I currently have it at 20 with a couple of relevant illusion perks. Is that really the highest it can be?

Also is it known if any human perks affect the vampire lord form? For example does 1 handed affect damage, light armour affect armour rating or dual flurry affect melee speed etc?

im not sure about your first question ( sorry ) but when it comes to the second question i think its alot like lycanthropy were 1h does not effect your claw attacks or anything of the sort, now with the VL radiant quests you get 2 items that do carry over to your VL form.

Ring of the Beast - +100 health and you do more melee damage.
Ring of Erudite - +100 Magika and your Magika regenerates faster.
Amulet of Bats - Your Night Cloak of bats now drain health ( not alot )
Amulet of the Gargoyle - When you use your summon gargoyle spell it summons 2 instead of 1.

Hope this helps

How do you garantee a power attack bite in vampire lord form?

make sure they are low on health