1. - 36 minutes to simply reach 25000 feet at normal climb speed, or to actually get to 25000 @ 395 mph?
That's the speed you can expect at 25,000 ft. There's no climb information on that data sheet.
2. - How much fuel is generally spent taxiing and warming up for interception missions, medium-ranged, and long-ranged escort flights?
From the Pilot's manual at 11,000 lbs adding warm-up, T/O and climbing; fuel used to climb to 25,000 ft, would be estimated at 44 gals. and take 18.5 min.
I can't find the Fig. 53 they say to look at for the warm-up and T/O.
Clean means a combat ready aircraft with no bombs or drop tanks. Usually it means no racks for those also.
Hope that helps you.