In a progressive league, I've got a very deep bench of pinch hitters, and a very middling pitching staff and bullpen, so I would like to pinch-hit for my pitchers very aggressively ... anytime after the 3rd inning when we have a rally going offensively, and pretty much EVERY time after the 5th or 6th.

I have set my pinch-hitting aggressiveness to 5, however I can't seem to get Sparky to follow along with the rest of the plan.  I've set my pitchers' target pitch counts low and maximum pitch counts higher, and set their pull ratings at 4, but if he just brought in the pitcher in the top of the 7th, he'll let him bat in the bottom half in most situations.  I'm afraid if I set them all to pull at 5, he will just make lots of pitching changes mid-inning, and I won't have enough depth to use my pinch-hitters.

Any advice from the board?

Make sure you have the pitchers PH box checked on the advanced settings page.  If that box isn't checked "sparky" won't pull the pitcher for a P-hitter.

Everything I just wrote to you got cancelled out when I lost internet for a moment. Let me see if I can reproduce the kernel of it as I have to get back to work...

I would suggest staggering the RPs appearances by one inning as well - one in the 4th, one in the 5th etc. so you don't risk having one in with no one to relieve him an inning later if you wanted to pinch-hit for him. And set the pinch counts for relievers high enough to finish an inning but not so high as to risk them pitching more than one and ending up with those mid-inning pitching changes you don't want. Say 20 given that they are not great pitchers and 15 might not be enough to get through an inning in many cases. Trial and error then to adjust.

This approach reminds me of an old trick of Earl Weaver - he used to have a good hitter at the top of the lineup at SS and then after he batted in the top of the first, put in Mark Belanger at the bottom of the inning at SS. The league passed a rule against it, but that rule IMHO is of dubious "constitutionality".

Weaver also used to put in a pitcher at DH at or near the bottom of the batting order. If his hitters drove the SP of the other team from the game in the first inning, he could then put in a right or left-handed DH depending on who the reliever was without wasting a position player for that game who was otherwise available now for pinch-hitting late in the game if needed. 

They made him stop without a rule on that one, something about it distorting batting statistics, but I am not sure how that supposedly worked.

The last one distorts batting statistics by crediting pitchers with extra "games started" as hitter (and taking them away from the hitters) -- but more importantly, subbing for the DH in that manner creates a pinch-hitting opportunity, crediting the hitter with an unwarranted "pinch hit" if he gets a hit.