It's all up to you really, put i would probably go with 15x rates, and 10x SP, also if you could only have the server up 6 days each week, i would close it on Monday, even tho i prefer having a server closed on the weekends, due to that me personaly often don't play as much on weekends, but there is of course a lot younger players that might not "party" or whatever they do on the weekends, and rather stay home playing.
Of course having the server up 24/7 would really be the best, also a idea is if the server is down on let's way Monday, are you able to check server files etc, make updates, check bugs? If so you could really take care of bugs, having 24 hours each week to check.
This is of course only my opinons, best of luck!