I got to Master (and very nearly tour master) with similar clubs to what you have there.
I would recommend what some other people say. 9 holes is better than 18 - my best score over 9 holes is 27 and have hit 30 and under dozens on times on pretty much every course.
However, over 18 my best is 58 and have only ever hit 3 rounds under 60 - all on St. Andrews which is the easiest one. So that will help get your scores down.
Also I tend to do worse in multiplayer rounds. Although I almost always finish under par I also very rarely hit 30 or under in them mainly because it's hard to get into a rythem. In a solo game you can play at your own speed and play shot after shot whereas in a group game you might be waiting for several minutes before you get another shot.
As for clubs - the G20 level 59 clubs are excellent - they got me to Legend but as you are level 70 I would maybe wait. The higher end G20s (level 83) are excellent. I went with the driver and wood (lvl 81) and the rocketbladez irons. I use the max putter now, but the nike lvl 77 putter is probably better if you are not good at hitting the ding. I did well with the lvl 35 ghost spider and used it for more than 40 levels.
The main thing is practice. I recommend you always use a ball with the same amount of feel - chopping and changing will not help at all. 2.5 feel is good because there are cheap balls with 2.5feel and also arguably the best value balls (Cally 250c) also have that.