Tannin in red wine

It is a balancing act. What is the pH and TA. If the acids are high, then the tannins really exacerbate the harshness. If the acids are on the low to moderate side then you can have more tannins without excessive harshness. I am learning this the hard way myself.

Try a bench trial first. Don't add it to your whole batch until you experiment with a small amount.

As for the ML, it is added by many not just to reduce acid but as an insurance policy against spontaneous or self starting ML which can occur post bottling - not a good thing to have happen.

Since a lot of wines will go through ML if you add it or not, it is a good idea to add a good strain of it as opposed to letting mother nature use whatever is there which may or may not produce what you want.

If you do not want ML to occur on its own, you are probably going to want your SO2 to be more than what you have added thus far. Of the 60 ppm, about half if it is going to be bound.

The California Wine Institute proposes an upper limit of 175 ppm for reds and 225 ppm for whites. The FDA allows up to 350 ppm

Here is a good reference:

While a lot of this is pretty advanced stuff, you can skim through it and pick out enough to be of benefit to you.