How many mph and rpms can my car sustain if I'm going to be driving 12 hours non stop?

So I have a 2003 Honda Element awd 4 speed automatic. My car has been serviced and has been mechanically inspected. I just changed the oil 2 months ago.
The thing is me and a co-worker of mine are planning do do a cross country trip from new Jersey all the way to San Diego, Cali. This is going to be my first cross country trip and I have never attempted doing this in my life. The longest trip I've done was traveling from NJ to Miami Florida with my dad driving a performance car(Infiniti g37 that was just lease off the lot). However, my biggest concern is how will my truck keep up with traffic in some of the state's I will be traveling into? I mean my state the speed limit is typically 55 mph but I know that in most of the western states, the speed limit is around 70(I believe) but in some western states I've heard that on some highways, drivers cruise really fast as much as 80-100 mph. My concern is can my car keep up with traffic at these speeds for long durations at emperatures as high as 90-95°? This trip is estimated to take about 4-5 days along with the resting stops we will be taking but if we going to be driving for at least half the day, what speed cany car comfortably cruise at without having to worry about wearing the engine and transmission and still last me 350,000 or more miles?

Read more: How many mph and rpms can my car sustain if I'm going to be driving 12 hours non stop?