Thanks for the info Rocky. When you say "bulk" age, is that any different than what I currently do...that is leave the wine in 54 litre carboys in the cellar for one year before racking into one gallon and one litre bottles? That is referred to as bulk aging, i.e. aging in bulk in a 54 gallon vessel vs. aging in a 750 ml bottle.
(As for these other questions, you would get varying answers from people, but this is what I do and what works for me. Therefore, what I am noting here is my way and is a suggestion and not necessarily a recommendation.)
Few more questions for you...
-should I add Potassium Metabisulfite after the first racking? I would add K-meta (Potassium Metabisulfite) at the approximate rate of 1/4 teaspoon per 6 gallons. More precise wine makers would test for sulfites and add based on their results. A quarter teaspoon is a good rough amount if you are not being precise, i.e. testing.
-should I continue with air locks or caps once transferred to the cellar? Again, some people would say solid stopper, some would say with airlock. Personally, I use an airlock so I don't have to worry about significant changes in barometric pressure forcing the solid stopper out of the vessel when I am not looking. One the other hand, if you use an airlock, you have to check the liquid level from time to time to be certain it has not dried out and is letting air in the demijohn. Lastly, I prefer the S type airlock because I find the liquid in it evaporates at a slower rate than in the 3 piece design.
-should I age with wood chips? This is a matter of individual taste. I happen to like an "oakey" wine so I add oak cubes during bulk aging.
-what is the main reason that my wine never tastes like store bought? I would guess it is because you are a good wine maker! It always tastes like home made. (and it is!) What is the missing link? I have heard this comment many times as though "store bought" wine is the way "wine" is supposed to taste. Personally, I prefer the taste of my homemade wine to store bought wine. I know what has gone into it and what has not such as other varieties of grapes, chemicals, dyes, color enhancers, sweeteners, thickeners, et al, not to mention field mice, rabbits and snakes that happen to be in the way when the grape picking machine comes through.
You are Italian so I would wager that you also like to cook and bake (I know that I do). Is Ragu better than your pasta sauce? Or is the bread you buy in the store better than your own? My wife makes all of our bread and we refer to it as our "communion host." I'll bet you can make an excellent pizza that would put Pizza Hut and Papa Johns to shame. Do you like the taste of your wine? If so, you have succeeded in making good wine. If not, what is it about your wine you feel is lacking vs. store bought. If you can identify that, then that is something you can work to improve.