What percent of the time can a turn checkraiser beat TPTK?

I am not asking about every turn checkraise here, but rather the type that gives me the most trouble. Specifically, one when:

1. The villain did not show aggression on the flop.
2. The villain is a decent but not great player – maybe postflop aggression of about 1.5.
3. The turn card was not an overcard to the flop (in which case a checkraise with TPTK becomes much more likely).
4. The game is shorthanded (I play 6-max).

My guess is that the checkraiser in this situation can beat TPTK a significant majority of the time, maybe 75%. I would guess that the villain has TPTK another 10% of the time and is bluffing or has a random holding about 15% of the time. So I would estimate my pot equity with TPTK in this situation to be about 20%. This may be too low, because for example if the villain has two low pair, you have a lot of outs to improve, but the villain will often have outs when he is bluffing also. In general, does the 75% figure sound about right to people? The 20% equity figure?

If so, I get the following implication. When you call a checkraise on the turn, you will generally have to call another bet on the river to see a showdown. So you are committing two bets to a pot in which you have 20% equity. For calling to be EV neutral, the pot must be 7 big bets immediately after the checkraise, because you can count the villain’s expected river bet and your two calls in the final pot you stand to win.

Lately I have been folding my TPTK to turn checkraises a lot, and I worry that it is encouraging people to take shots at me. But I think if I use the 7 big bets rule of thumb, and I look for additional reasons to call such as gutshot straight draws etc., I will be calling enough of the time to keep people honest.

Does this seem like a decent strategy to people? Does anyone have any tips or insights on when a checkraise is more or less likely to be a bluff than usual?

Thanks!