Jack Keller used to have a website which I have bookmarked but he passed away and no one maintained it.
This is the pdf that home brewers put together based on the contents of his website; https://swguildpa.com/wp-content/uploads/2020/11/Jack-Keller-Complete-Requested-Recipes-Collection.pdf Try page 226.
Huge set of wine recipes using store bought fruit products, fresh fruits, wild fruits and more.
After searching for "homemade fruit wine jack keller", I found the link to the pdf here, https://forgedmettlefarm.com/2021/07/12/read-this-looking-for-jack-kellers-wine-recipes/
Guess I'll have to download the pdf and add to my cloud. If I still had a monochrome laser jet printer, I'd print out the 326 pages. My neighbor would love it. He has a little homemade wine recipe book that I guess is pretty popular. I'll have to look at it next time I'm over there. For all I know, it could be by Jack Keller.
He had no fancy equipment just some big jugs maybe a hose out the top.
Check out the airlock on the right. That U shaped dip would have water or wine in it to make the airlock. It works the same the odor trap pipe under a sink. The liquid prevents non-pressurized air from passing but in the case of an airlock for fermenting, pressure can escape by bubbling it's way through the liquid but no wild yeasts in the air we breathe are going to drift into the jug.
Your dad could have done the same with tubing jammed through a rubber bottle stopper and by having a dip in the tubing with liquid in the dip.
Less yeast or more sugar would make a wine sweeter and less potent. Taking it early makes it less potent, less dry and more flavorful but in my case, more flavor means more yeast flavor for that one week old stuff. At two weeks it's decent and probably closer to three weeks for no off flavor and still not dry I don't think. I've had maybe 2-3 glasses of wine in my life until I started making it so I don't know what's what as far as taste, aroma, body bla bla.