Welcome and congrats! I'm a recent Wrangler owner too so I can relate to the elation/confusion you're feeling.
I'm no grease monkey so the only question I can answer is about the acceleration and yeah, it's not unusual for YJs to be slower than a fat guy's metabolism above 50. My YJ is completely stock with the 2.5L/5-speed and while I can cruise comfortably at 65-70, trying to pass anyone is an unattainable fantasy, and trying to maintain speed on an incline requires a downshift. Your '88 has the 4.2 6 and believe it or not, it has less horsepower than the 4. That it has the 3-speed automatic doesn't help much. Its main attribute is the low-end torque, which makes it feel quick in stop-and-go traffic and helps get your through obstacles when you're crawling over rocks, but it's a turtle on the highway.
Also, when you look at the YJ, with it's blocky, rectilinear profile from any angle, it's the aerodynamic equivalent of a barn door, and it's going to be slower than most cars, regardless of engine, at any speed above 50.
That being said, it'll do most of the things any regular car will do. You just need to plan ahead a little more. And if you're anything like me, you'll learn to enjoy the more relaxed pace.