oil change

I just got the Scag Liberty with the Kohler 22hp engine and now have 9 hours on it. I need to change oil and filter, can I use syn oil? Can I use Mobile 1 oil in it? Should I use 10w 40 oil? Thanks for any suggestions on this, such a great mower.

In my owner's manual it shows 10w30/40 or sae 30 for my temperature I'm operating at. Which is the best to use? It clearly states right below the oil chart that multi grade oil will increase oil consumption. Should I go with the sae 30 then?

Was changing the oil on my TB-30R (2020- model 13A726JD023) and somehow messed up the internal threads when I was reinstalling the oil drain plug. Not sure how to fix this so any advice would be appreciated. ChatGPT suggests a thread chaser and if that doesn't work use a tap. But I have no idea...