Late to this party but long time instructor and owner of 1996 RPM Max I purchased new from NOC. And, have 7 kayaks including Remix 79 and Super Hero. That RPM Max is still one of my most favorite kayaks.
The RPM series is a proven kayak and should work to get you kayaking.
Second the need for good instruction on low risk runs.
The RPM series works great when the boater keeps their chest forward, that is if the boater leans back that transfers boat trim to the stern which creates water over that flat tail section and a wobby kayak. Most issues with RPM's are cured by chest forward semi erect posture.
So make sure you understand how to set in your kayak. IE weight balanced on butt cheeks, chest forward a bit - bending at the hips and feet comfortably on the foot pegs.
You mentioned feet going to sleep etc. You cannot be comfortable and balance your boat if the outfitting is off. The RPM outfitting is pretty simple. But make sure the hip pads are foamed out and provide secure but not binding support to the upper part of the hip. Make sure the back band is snug and provides good support. I replaced my RPM Max factory back band with one of the aftermarket brands, ask your local outfitter for help on getting the right one. You mentioned feet going to sleep, this maybe caused by too tight hip pads or front of the seat too high. On my RPM Max I put on the stick on seat pads. Again check with the local outfitter and order what works.
The RPM series is one of the easiest boats to roll I have ever had. But as mentioned before you have to have good outfitting to do a decent roll especially during the learning process.
My RPM Max is one of if not the best surfing kayaks ever for me. For a newbie, surfing is one of the first and most fun play moves they can make and good front, side and back surfing sets you up for more advanced play moves as far as the comfort level is concerned.
So bottom line suggestions. Get that RPM outfitting to fit. Learn proper posture and chest forward bending from the hips when paddling the boat. Learn to roll in a pool with good instruction. Get a nice diving face mask to wear while learning the roll as this cuts down on problems with water in the nose and lets you see what is going on) Progress to class 2 runs and get comfortable paddling forward, good "J" leans to carve turns, eddy turns, ferry moves and easy front surfing. Do this then move on to class 3 runs.
The RPM series is a great way to get comfortable and learn to kayak. They are cheap to buy and easy too paddle. Learn to paddle up to easy class 3 runs then look around to maybe buy a newer boat design. I can tell you from decades of buying boats, if the outfitting is right, your problems are not the boat and buying a newer one is not gonna solve your problem. Get the basics down in that RPM before you go blowing money on new boats.