What you're missing is Mile Saver (or whatever CO calls it) awards. You're being quoted Any Time awards. Naturally, the cheaper ones are much more limited in quantity.

You can go on United through CO also, you can go on ANA. Upgrades could also be done as you suggest, but you have to find the inventory available. I'll leave it to MR/CO/ANA experts to tell you the best way to find them other than the respective websites (which I understand work well). On CO there are two columns under each class of service on an award ticket, the miles required are listed right there as well, the one that always says 'not available' is the one you want . Just change dates and destinations til you find one you want. Or try calling and have them do it. CO will hold a res pending MR transfer (last I heard, long ago).