Welcome to the forum!
I'm sorry to hear you're having issues with your 709. The slam fire one is particularly troubling, hope that gets resolved soon!
I know that I had to consciously use just the pad of my finger on the trigger; if I inserted my finger to the first joint, I was pushing it low/left consistently. After concentrating on using just the pad, I got it corrected to point of aim pretty much every time.
Keep us updated - the 709 is a great carry gun (I carry it all the time), but they do take some getting used to. And, if it indeed needs repair, getting it back to Taurus is the best choice. They will make good on it.