The 1x1 rib as well as the smaller needles make for a dense, very warm hat. The stitch is also super stretchy so the pattern is written in one size with changes to the length to accommodate different sizes.
Because the ribbing will stretch to fit, the exact gauge is not crucial. As long as you stay close to 30 – 32 sts per 4”. (unstretched)
The 1x1 can become tedious, but the end result is well worth it! Try adding stripes in the brim. It can be a good way of playing with the design.
I found a version of ssk that works better for me, looks neater. When I get to the ssk, I turn the first stitch front to back and return it to the left needle. Then I knit two stitches through the back loop.
The left slanted decrease looks less “wonky” for me when done this way.