Capped at 40% for each element. I don't know of any cap with Straight +Absorb.
As for an FAQ... there are sources all over the place but not one place where you can get Absolutely all the information you need. There are just so many topics and different ways of approaching them (Statistical, Game-Play/Strategy)
Oh, there are Huge advantages in having +Absorb. Of course, they do Much better with High resists.
As for the Rising Sun, it's not a % absorb.... it's a Straight absorb. There IS a difference.
First, you took 200 Damage because the Meteor drop does TONS of damage at once. So with only rising sun, you cancel only a small amount. Standing in the fire is when he healed, because the damage is done Per Frame. This means +Absorb does a LOT more because the damage is Divided by 25 for the damage it says per second.
Dwarf Stars helped a lot with the inital blast because they take %. After that, the Rising sun healed you with minor help from the Dwarves.
If you took off Rising Sun and you stood in the Meteor's fire, you'll see your life still goes down (Albeit much less than if you had no absorb)