I started commuting in May. I'm learning some of your same lessons.
So far, my commute is multi-modal (bike from house to MTA Park-n-Ride 3.8 miles, bus 8 Interstate miles, off, ride another mile to the office).
I've ridden the complete route via bike only 1x (15.2 miles). It can be done, but I'm still exploring alternate route options that will be flatter/safer. Nashville has lots of hills and the mindset of those in motorized vehicles can vary widely when it comes to sharing the road with bicycles.

I bought a change of clothes/shoes to leave in the office. I haven't had to wear the clothes yet, but I do utilize the shoes.
There's been little rain here this summer. I was out of town the week it did rain. I've only gotten wet once, on the home one hot afternoon.

Still learning..