I ride in Big Bend National Park a couple of times a year. Just got back Monday, 11/09/15. The above post are correct as to where gas is available, but if you miss one of them you are pushing your bike (not a good place to have to push).
River Road through the park is about 60 miles, but it's 40 miles from Study Butte, 30 miles from Panther Junction, and about 20 miles from Rio Grande Village. Sounds like your bike has the range to ride it, but with zero margin for error. River Road is about the most technical road in the park, but well worth the ride.
Big Bend State Park is located between Lajitas and Presidio off of FM 170 (also called River Road, but it it the paved one and a great riding road). I have not ridden there for a number of years. At one time they had restricted motorcycles from entry. Don't know if you can ride in that Park or not.
As for riding the slab (I-10) to get to Big Bend, it is 103 miles between Ozona and Ft. Stockton. I would not ride your bike at the 80 MPH on I-10; even at 70 the big trucks will just about blow you off the road. And at 70 you probably won't get 90 mile to a tank of gas.
As for where to stay; Big Bend Motor Lodge in Study Butte had rooms for $89/night two weeks ago. The Eldorado in Terlingua Ghost Town is about the same quality and rooms there are about the same price. Lajitas has very nice accommodations, but I can't afford them. The golf course there is fantastic, and over $100 for a round.
Oh, get a bigger tank.
Hope this help. If you have never ridden that area go do it...
Later, Bud...
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