I think you might try "bench testing" your wine. What do you object to the most? Figure that out and work to alleviate that single issue. Let's say it's the "sourness." You might try sweetening the wine with some simple sugar syrup (2 parts sugar/1 part water, simmered & cooled). Set up three or four glasses with 1 ounce of your wine. Put measured amounts of the syrup in the glasses, stir & taste. You can start out with a dropper, and do 2 drops in the first glass, 4 drops in the second glass and so forth. Sometimes a little sweetness can bring back the grape flavor. You just don't want to overdo it. More astringency can be had with tannin additions. Again, don't overdo it. I gain mouthfeel with the addition of glycerin, which also helps with the apparent sweetness. In my view, a little bit goes a long way. Oak is a style choice. I oak some and leave it out of others. If you read the winemaker's notes on the commercial Malbec you like, you may find out if they used oak barrels or not. Use this knowledge to tailor your batch.