The descents you are taking don’t really matter. For flat stuff, you could probably get away with putting your foot on the tire. Riding in traffic is a different story but on the open road or better yet, gravel road, no biggie.

The tires will make small a difference but it’s probably not enough to break the bank over.

If you’re riding gravel tires around 40-50psi, you might consider doing a ghetto tubeless setup on your bike. It used to work great on mountain bikes before tubeless became standard. I wouldn’t do it at road bike pressure though.