So you're allready on the road, so I'm too "late" with the cheers
Going long distance means "only" having trust in your vehicle (and it doesn't matter if it's new or old). So put some emergency spares, some tools, etc. and be sure, that the car is in a good condition (I assume that) and then it goes anywhere. The TLCs where designed to do that.
But know your car, like how much oil it consumes, have a look at the coolant fluid once in a time, ect.
When I bought my truck, I was a little bit anxious as well and I told the insurance broker to include the road side service incl. tow-back infinte (and in Brazil this can be also 5000km

). But I repaired everything, got used to it, no open topics regarding maintenance, ect. I have a extended tool and spare-kit and I know what to do with it. The best thingis anyhow to fix all problems right away in your own garage, usually that's the best prevention against brake-downs.
Now I would never mind to go on a long distance trip with my truck, just check the oil/coolant and go. And I would know, how much engine-oil I need to take along with me to refill during the trip.
Cruising speed: I think you're doing right. My engine has also a range between 2100 and 2300 where it feels comfortable, I can tell by the vibration level and also by the consumption. This will be around 50mph and that is the cruising speed for the highways. Off the highway I go almost the same speed, depends on the situation. A old Landcruiser is not made for the highway