I have had very good success canning stuff by re-using pickle jars and spaghetti sauce jars.
I get a good seal with the original lids and I love hearing that ‘pop’ when they cool down.
Clean them well, boil the lids for a few seconds. I sometimes don’t even use a canning pot to steam them for 20 minutes, but it would probably be better to do that.
I make chili, clean and pre-heat my used spaghetti jars, and use a large funnel to put the hot (boiling) chili into the jars, carefully close the lids (using a towel) and after a few seconds release the pressure and re-close, and do that over and over until no more air pressure is released. Then I set them upside down, to make sure the lids stay hot for a few minutes.
Then set them right side up, and wait for the ‘pop’ of the lids. Any that do not seal and pop (rare) I just refrigerate and use right away.
I am a scientist by profession and training so I watch carefully to measure success.
If I was REALLY REALLY serious about canning and saving a particular batch, I WILL use the canning pot and steam them for 20 minutes, before I close the lid.
I can on average about 400 lbs of tomatoes alone, every year plus various other fruits and veggies. After varying levels of success with previously used containers and lids over the years, I use as many glass lids with rubber rings as I can. When I run out of the retaining rings for glass lids, I go with the Bernardin lid sets.
Pickle jars with original lids and the like are not reliable enough. I have a ~0.1 % failure rate with Viceroy rings or Bernardin lids, but a near 15% failure rate re-using factory jars. That is WAY too much waste, as you can only eat so much of the product while processing...
As a scientist you know that once the product is in the jar it starts cooling, and that decreases its volume, so why did you say you are “releasing the pressure” after filling?
If the jar is hot, and the product is hot, and the lid is hot, where is the “air” you are letting out coming from? All you are doing is letting air in, from my experience. Unless I missed something, which is quite possible.