Wow! That's an amazing first ride!! Way to go!

At the start of riding, IMO, you shouldn't worry about things like cadence. You should just get out and enjoy riding. Some people are built to spin (higher cadence) and some are not. The key is to do what feels best to your knees. And as you ride longer, you will start pushing bigger gears at higher cadences naturally. You may never spin at 90+, but if you listen to your knees, you'll do what your body is intended to do. Work on it some, but mainly enjoy the ride.

I remember back when I used to ride before my hiatus, it was all the rage to spin like Lance in the late 90's. He maintained cadences of 130+. Everyone was spinning like Lance. I'm sure there were some knee injuries, too.

As for numb feet, it may be a matter of getting used to being clicked into your pedals and remembering that you can still move your feet some (assuming your pedals have some float). I adjust my straps a time or two during my rides, too. You don't have to keep the straps the same throughout the ride. If your feet start to go numb, try to wiggle them some and maybe loosen the straps a mm or two. Good luck and way to go on a first ride!