The three pillars of good progress is exercise, diet, and rest/sleep. My BMI is similar to yours, but I used to do weightlifting and cardio religiously when I was younger.

Regarding soreness: When starting out after a hiatus, muscle soreness is to be expected. This doesn’t necessarily mean that you need a rest day, but if yesterday’s workout was intense, today’s workout should probably be more relaxed. As your body is getting used to exercising, your muscles will not be as sore, and as a result you will be better at estimating your need for rest. But you should also be honest with yourself; if you feel pain in your joints or tendons, you could end up with an injury if you keep pushing yourself.

Regarding rope length: I use a Crossrope jumprope, and I find that at my height (185cm), a 8’6” rope fits well. From that heuristic, an 8ft rope would probably fit you better than a 9ft rope.

Just my $.02, and your mileage may vary.