Looks like luck to me...
You failed to mention a few aspects of the game to allow for a complete sim. I assumed you play heads-up and get 7 rounds per deck. I also assumed that the rules are SD, H17, DA2, DAS, 6:5. If these assumptions are in error, please post the correct information and I'll rerun the sim.
I used CVCX to sim the above-mentioned game, using a 10-count running count system with tags of -1 for all X's, and +1 for everything else. I assumed your system is like this, since you mentioned taking insurance at +4. Again, if I am incorrect, please let me know and I'll make the necessary corrections.
The only index plays are those you mentioned: take insurance at +4, and stand on 16 vs. X, 12 vs. 2, and 12 vs. 3 at RC>=0. Otherwise, I used basic strategy.
With a 5:1 spread, CVCX shows the optimal betting to be 1 unit at RC<=+11, and 5 units at RC>=+12. This, however, is not sufficient to make the overall game +EV: your Initial Bet Advantage is -0.259%. Even if you get 9 rounds heads-up (good luck finding THAT game), you're still in -EV territory with a 5:1 spread.
If you increase your spread to 10:1 (with 7 rounds heads-up), then you're in +EV territory: IBA = +0.458%. You'll place your 10-unit bet roughly one-sixth of the rounds.
I know you said you didn't want a suggestion to find a better game... but, really, find a better game ;-)
Hope this helps!