Just a question...in case you do lose clutch functionality, are you able to shift without the clutch? Clutch-less shifting isn't very nice to the syncros, but if you're careful about it, you won't do too much damage...and since you're running on the freeway, you shouldn't need to do it all that often, and it'll keep you from being stranded. If you haven't done it before, it might be worth it to practice a little bit...it's really a matter of trying to match engine speed to the speed the tranny's spinning at, and is an art form as much as anything else
My clutch slave cylinder failed in 2003, and I wound up driving to Napa and back with no clutch...while towing the trailer from Hades
With the trailer in tow, I had to shut the engine down every time I needed to stop, and then start the truck in gear (read: the starter was moving the truck and trailer!) when I needed to get going again. It was exciting, but was able to pull it off...and I got another full year and a half of life out of that starter, before losing all 8 glow plugs and (stupidly) cranking the engine over more than I should have...