Afaik 100 effective wpf makes your weapon as effective as it is listed on the site, so with 1 wpf you do 15% less damage
Which means that 150 wpf will make you do 107,5%, which means there is no full potential as you did state before, but this is nitpicking.
WPF helps 1h a lot. I disagree with those that say 0 wpf is ok for 1h.
Nobody is saying that, 0 WM, which means that you still have like 115 wpf.
And 15% damage increase for every 100 WPF (7.5% per 50WPF is actually very good, that's one more Power Strike basically) but I do not believe that is accurate, as I was under the impression WPF x PowerStrike (minus other variables like enemy armor/health and soak) are what takes your damage into consideration.
Gaining 50 wpf does in fact cost you 6 attribute points though, which is quite expensive compared to 1 attribute for PS. For the same cost you can get 12 hitpoints.
This is the wpf and powerstrike relation
(WPF*0.01*0.15+0.85)*(power_strike*0.08+1.0)
Which gives me 1.56 for 100 wpf and 1.67 for 150 wpf. 1.56 and 1.67 is a 6.6% difference. Of course due to the multiplicator the increase gets lower at higher wpf comparisons, but because the wpf value is such a small factor in the formula, 15% per 100 is a close enough estimate. It is actually only 13% when going from 100 to 200.