First time IFer here

Hello all, I'm a 35year old, 5ft 10" male, weighing in at 200-205lbs (depending on the meal I just ate). Over the last few years I have slowed down on my excursive I was formerly an adventure athlete (triathlon, rock climbing, backpacking), these days my main source of "exercise" is scuba diving and I've recently become a father for the first time to a beautiful baby boy (currently 4 months old). Recently I have noticed I am having chronic low/mid back aches and intermittent knee pains. My goal weight would be about 175lbs, When I was training for triathlons I was working out 40-45hours a week and weighing in at 165lbs and I looked unhealthy skinny. I don't want that, I want to be a healthy weight with a strong body and mind to be able to chase my kid around and should I be lucky enough to have a second kid chase them around too. I would also like to get back into enough shape to run a few half marathons this year without knee and back pain. ​ I'm really not too sure where to start with intermittent fasting, I know my eating windows will shrink and I shouldn't really restrict calories. Should I start out with a 12/12 schedule and work up to a 16/8 over a few weeks? My biggest guilty pleasure is the 2-4 drinks (beers or cocktails) with my wife after the baby boy is put to bed to help wind down for the night, this usually leads to evening munchies. I'm also okay with switching out beers and cocktails for a small pour of whiskey on ice or neat (I know its not perfect but its better). ​ Any tips, tricks, suggestions, or kind works would be much appreciated.