hello and congratulation for your new gremlins.
I cannot answer all your questions abbout diet since I am not familiar with OHPW, but I can shed some light one other topics.
1) Male gliders usually reach puberty around 6 to 1 months, but some can start as early as 4 months old, so I'd say not later than 3 months old if you don't want to risk seing joeys.
3) Some diets do need to add calcium and vitamins, it is called for in their feeding instructions, other diets are "complete" as the vitamins and calcium are already included, I think HPW diets are completes since the vitamins are included in the wombaroo HPS. Not sure about the calcium though, but I'm sure other people can answer on that point.
4) During their 1st days in a place, they are discovering their environment, so their behavior can be totally different from what it will be once settled. It is not uncommon for gliders to not eat well during the 1st days (some do, some need to settle in), remember everything in your place is new to them, and scary.
5) It depends on the individuals, some can be active in a lighted environment, most however will just freeze and seek a shelter. Mines are not active as soon as the light is brighter than a computer screen.
6) I don't use bonding pouches, the few times I tried it's been really difficult to make them go in, I think it's something they get used to with time and practice, but it's not spontaneous.