How or what about abrasion resistance when passed through the stanchion or ring?
I've had Amsteel lifelines for just about two years now (courtesy of Brion's suggestion and a splicing lesson), running through typical stanchion through-holes. I see no visible chafing. I haven't been hitching my fender whips to the Amsteel however, so there isn't a) the chafe of the fender whip rubbing on the lifeline, and b) movement of the lifeline caused by fenders moving against the dock. I don't know if either of these would cause significant wear, but I've been caution about it and am quite happy so far.
I will second michelg's praise of the Splicing Wand.
The gates will be interesting. If I use 72 x dia. bury, that will be at or greater than the width of the gate assuming 5/16" or 1/4" line.
In that case, you can make a grommet, which will give you 2x the distance for your bury. Ring-hitch (or is it Cow-Hitch? I know it's not Lark's Head) one, ah, "end" of the grommet to your pelican hook, and then hitch the other end to your stanchion by passing it pelican and all through the bight. I did this. Since in my case, the gate is also the helmsman's backrest and keeps him (i.e me) from falling overboard backwards, I'm happy to have the double thickness.