AT-ART9 cartridge on Marantz TT-15s1 - I don't think I'm getting the performance I should

Some time ago, frustrated with what was likely cartridge alignment issues coupled with worn LPs, I upgraded my cart and sold my VPI Scout turntable and now have an AT-ART9 on a Marantz TT-15s1.  That turntable was recommended to me because of its relative simplicity in cartridge alignment.  I've been really enjoying the fullness and clarity of the AT-ART9 on some LPs.  By "some" I've found that I mean records without obvious wear and that are cut on the quiet side. 

What's bugging me is that I feel l am getting far from the best out of this cart.  I have read that it is REALLY finicky to dial in for best tracking results, and my cart doesn't appear to be tracking a lot of records well at all.   I started buying a lot of vintage sealed records to eliminate groove damage from being the issue.  But I've noticed that almost every album that's cut on the "hot" side plagues me with distortion that gets worse as the stylus gets nearer to the inner grooves.   For example, I've played a lot of '80s hard rock and metal, and I can almost count on any album from that era cut on the Atlantic label in these subgenres to give me distortion that's clearly due to mistracking. 

What may set me apart from others on this forum is that I don't have buddies with comparable systems in driving distance from me where I can bring my records to hear on their systems, so I really have absolutely no basis for comparison.  I have just read people say that they have never heard IGD with this cart, whereas I hear it on many 75% of my LPs.  I don't have any problems with known audiophile pressings though, like new stuff cut by Chris Bellman, Kevin Gray, on the Classic Records label, etc. 

I used to have my cart professionally set up, but after finding that my dealer totally bungled the setup on my VPI the last time, I decided to learn how to do it myself.   I got myself several Stevenson protractors and a 3x magnifier so that I could see what I was doing, and it absolutely looks to me like I've got my cart aligned as perfectly as one can get it using the null points on the protractor.  

I *do* however think anti-skate is causing me problems with my configuration.  I did have it set too high and that absolutely caused me more distortion in the inner grooves as well as a large number of records "sticking" (i.e. repeating instead of skipping forward).   But even after adjusting this heavily, I still find that in the rare case that I have a used record that skips, the tonearm "sticks".   That, to me, suggests too much antiskate, but I have set the antiskate to be almost as minimal as possible from the best that I can tell. 

Absent of a local dealer that I've yet to find who I can trust to identify and fix this issue (especially since the nut used for setting antiskate on the Marantz is so loose that it would easily change while driving my TT back home), I'm at a loss having done everything I can do to possibly fix the problem. 

Based on what I'm saying here and your experiences, am I most likely missing out on the supreme tracking abilities of this cart, or is there just a lot of really bad pressings and damaged used vinyl out there?   And if it's the former as I suspect, is there anything about the Marantz's tone arm that suggests it's not up to the task of supporting this cart?