I have a similar mixer/spiral hook and use stone bottom gas ovens (with top and bottom gas elements) at about 325 C also. I have a 57% hydration and cold ferment with a freezer to refrigerator (in reefer 12-18 hour ferment) cycle.
For my mixer, Low is 110 RPM, Medium is 200 RPM and Hi is 420 RPM. I think that is important to add to the discussion.
I mix on "low" (110 RPM) for my entire mix. I do not change speeds.
I start with (slightly chilled) water, sugar and salt in the bowl, then add about 70% of my flour. I add IDY then add another 20% of my flour and start mixing. I add the remaining flour after a minute as the dough mixture begins to collect. After a ball begins to form (about 2 minutes), I add 1/3 of my oil to the bowl side, and add the other 2/3rds in two more steps about a minute each later.
I adjust the height of the bowl (usually downward) to get the best mix as the texture of the dough changes. I adjust that height as I watch the dough to ensure the complete mixture is being folded properly.
I mix on Low for about 6 minutes after the complete ball is formed, but I measure the temperature to be sure. I use a finish temperature of 29C for my dough. It's a relatively fast mix. I think spiral attachments are more efficient than old fashioned dough hooks.
The mixture feels a little moist, but is not wet or difficult to handle. We measure and form quickly, brush on vegetable oil on the ball and drop it into a small plastic bag. We squeeze out the air, twist the bag closed and put the closure under the dough ball and put it into the freezer, all very quickly. I get no freezer burn or frozen moisture in the bag. We only keep it in the freezer for a maximum of a week.
We open the bags to give some room for expansion as we transfer to the refrigerator, but still tuck the opening under the ball. We use them cold from the refrigerator and do not bring them to room temperature. They are the most flavorful on the second day, but still useable after one day and on the third day. We don't use any after that.
My recipe ends up as a mix between a neapolitan and NY type. It has leoparding and a lot of air holes around the edge, but is slightly firmer in the center so it can support more toppings than just fresh mozzarella. We're a takeout/delivery business.
We cook directly on the stone. Bottom heat is 200 C and top heat is off to start. After 3 minutes, we turn on top heat and total time is about 5-6 minutes, depending on toppings. Margheritas go in with just sauce, then fresh Mozzarella added after the 3 minutes and flash cooked for the last 2 minutes.
I don't know if that will help you, but it explains how we do ours.