put your blade all the way up
Reading that just gave me the willies. Kickback is real, I’ve seen it and I’ve also experienced it. It will happen so fast you won’t even know what hit you until you feel the pain and hopefully haven’t lost any body parts. Crankin the blade up greatly increases your chances of kickback especially with a 12” deep tread where you may be twisting the tread in an attempt to follow a scribe line. I highly recommend renting a miter saw with the capacity you need or even using a skill saw with a home made cutting guide. You can make one in about a half hour for less than $20
If you do decide to wing it with a table saw, a sharp blade will do wonders and you only need it 1/8” to 1/4” higher than what you’re cutting.