The whole inches-per-gallon rule doesnt really hold - because some fish (as stated above) like tangs throw those averages out the window. The tangs inches has more to do with swimming room.
It also has alot to do with how well you take care of your tank, and how good your waste export is.
In my 75 (90 total) I have:
1 Regal Tang (juvi - this guys getting me a tank upgrade soon
3"
1 Copperbanded Butterfly 3"
1 Occ Clown - 3"
1 LawnMower Blennie - 3"
1 Green Mandarin - 3"
3 Green Chromis - 4-5" total
1 Yellow Watchman Goby - 2"
1 Green Clown Goby - 1"
1 Neon Goby - 1.5"
1 Royal Gramma - 2"
Holy crap i didnt realize I had 12 fish! + 2 Shrimp! If you include the shrimp I probably have nearing 28" of fish or so. But the majority of them are small fish - and I have zero aggression in this tank (aside from the clown chasing a chromis every now and then).
My nitrates have been zero for so long I rarely test for them anymore.
My export system is 80lbs of mature live rock, EuroReef RC135 recirc skimmer ( this thing seems so efficient that it seems i can overfeed all I want with no ill affects concerning nitrate spikes), 2" sand bed, small fuge with a tiny bit of halimeda, new phos reactor (I feed alot and need to export phosphate and silicates from my food). Oh - and plenty of flow with no dead spots in my tank - the majority of my rock is supspended off of the sandbed by stacking and PVC frame.
I have a dozen or so SPS, and a dozen or so LPS/Softies that are doing fine.
Your inverts make your livestock list seem larger than it really is, I would say if you can keep your params in check then go for a couple more small fish. I personally would rather keep many small fish than a limited # of small fish.