When is it open during the week? Right now it's only open on weekends.
Not now, I believe. Now since Halloweekends is here, they aren't open during the week.
On your Fast Lane+, I can see it going up on Saturday. It is the busiest days during Halloweekends, of course.
I am not sure where to get them outside of CP, I believe it is just there. Don't think you can buy them from Meijer, Kroger, AAA, etc..
If I were you, just to save the extra dough, get to the park early. Maybe see if you can get early admission tickets. Right when you get into CP, go straight to either (a) Valravn; (b) Maverick; (c) Top Thrill or (d) Gatekeeper. You will knock one of those out right away with very little to no wait. Then go to the next one (
maybe plan it so you can go to 2 that are right by each other, like Top Thrill and Valravn). Then use your Fast Pass to ride all the rides you want to that are covered under the FP. When it gets later and the haunted stuff starts opening, hit up Maverick, some more on your walk back to the front of the park, then on your way out, the very last ride, make it Gatekeeper since it is closer to the exit.
That is what I would do, but if you can fork out the extra $50 or whatever it is for the FP+, do that. And as STEREO said, if you plan on riding coasters multiple times, especially those 4 that aren't on the regular FP, maybe it is worth it.
A very underrated ride which is by the Gatekeeper is the maXair. Wait is never more than like 10-20min.