Moka pot is probably the hardest common brew method to get right. If everything is coming out as sour, from specialty roasters to super dark grocery store beans, it’s most likely a process/technique issue rather than the brewer. I can give a few suggestions:

1. Explore grind size more thoroughly. While marketing says it can be used for moka pot, it’s probably stretching its limits and I wouldn’t trust published chart numbers on range. Typically, if it’s sour, it’s under extracted and you should go with a finer grind size and increasing the amount appropriately. In another comment, you said going coarser gave better results so can try going even coarser as it’s possible it’s to too fine and over pressure is causing some form of channeling. Also, probably do a once over on your grinder, making sure everything is put together well and is zero’d properly.
2. Double check the recipe you are using matches your pot size. Moka Pots come in different sizes so using a recipe for a larger/smaller pot could yield poor results.
3. How are you applying heat? Constant heat until it’s done or taking it off/on based how it’s brewing? What does the stream of coffee look like, is it smooth and almost syrupy or bubbly and violent? As long as you are starting low and the stream is coming out smooth, I probably wouldn’t worry about heat much. If it’s coming out fast and bubbly though, turn down the heat or remove it from the heat completely when it starts going.
4. Make sure you aren’t over tightening the pot. While it should be hand tight, you shouldn’t need to crank it super hard. You did mention that 5-10 ml leaks out which shouldn’t happen but could if its too tight due to overpressure.