1. Get a ptera or Tape whichever you prefer. Before grabbing egg make sure you a trap for the wyverns chasing you and an escape route.
2. They will always aggro on you.
3. Flying far enough from the trench should make them deaggro. Or find a nearby dino.
4.Just get between 20-30 in a circle of the torches.
5.only milk nothing else till adult.
6.Females only and only go for alphas if prepared. for normal females it's always five milk. alphas have 50.
7.the total time is 3days 20hours 35 minutes and 32 seconds if on offical settings.
8.I would go for lightning if you want a dps one. fire for death worm hunting(though lightning works too) poison if you are doing pvp(it can one shot a rider off or at least stun them) Ice is more pvp or for just a general use its breath is good for slowing down stuff but otherwise is beat by fire and lightning.
EDIT: This is milk info taken from the wiki:
The babies cannot be fed Raw Meat like any other carnivore; however, their food drops a lot slower. They require Wyvern Milk to increase their food and may ask for it when imprinting. Wyvern milk gives 1200 food to the baby Wyvern. The Wyvern Milk is obtained by knocking out a female Wyvern or Killing an Alpha and removing it from their inventory. After one hour a wyvern will regenerate 5 milk.
A growing baby Wyvern will consume approximately 1 unit of food every 10 seconds, or 360 units of food an hour. This means that one feeding of Wyvern Milk will sustain a baby Wyvern for a little more than 3 hours.
An important detail about newly hatched Wyverns (especially at lower levels) is that even though the maximum food stated in the creature's statistics might be several thousand, the maximum food the baby can actually hold might be less than 1200 (the amount of food one Wyvern Milk delivers). This means that lower level baby Wyverns will never eat milk on their own, and will have to be force fed Wyvern Milk until they can actually hold more than 1200 food.