As far as a midrange to throw for long putts...you'll want to get the same putter in a lighter weight or just get a Rattler. You want something that will hold a line with no effort and that will fly straight with ease.
If you don't have the arm to throw ~350 consistently in all conditions throw after throw a Nuke will not be a good choice for you. You'll want to get drivers that are understable to start and then you can move to more stable stuff. The thing to keep in mind is that you want something you can control. Unless you're playing on courses that a lot of the pros play on (and even then) you don't need to throw 450+ feet. If you can learn to drive 300' straight and controlled and be deadly from 200' or less then that is all you need to compete at most any tourney you'll ever go to.
When running a long putt the last thing you want is a disc which glides a long way. You probably want a disc which doesn't glide at all so that when it misses (as most long putts will, even in the most skillful of hands) it stays close. Midrange discs have medium glide. Not the superior glide of a driver or the stunted glide of a putter. So a midrange disc doesn't make a lot of sense for a long putt except for those players who don't use putters at all.
The perfect disc for the long putt/ short run is the Rattler. The Rattler is a putter type disc with no glide and it has the ability to fly straight even if thrown softly. It does, though, require significant skill and touch to master. But since all worthy goals take time to achieve, there is no time like the present to start. If you have an aversion to the Rattler you can create a similar flight by taking a standard putter and breaking it in for many, many years. Then it will be almost as good as a Rattler. :)
The Nuke is a power disc which flies farther than anything else I have ever thrown. The Nuke wants to fly far and fast. If you have the power to use it it may be as magical for you as it is for me.
I throw Buzzzs for most of my midrange shots. I also like the comet in X plastic for shots that I need to turn to the right. Inside 100 ft, i turn to my Magnets. I keep 2 magnets for inside the circle putts, and 2 for everything 100 ft and in, up to the circle.
The classic Roc in anything but Star plastic is great, otherwise it is a stable pig. Which is good for upshots or headwinds. Some people like ridiculously stable putters, if that is the case then the Star Classic Roc is for you.