[Scimitar]

Always hard to answer, as things change all the time.

But my thinking is, an injury waiver might not be the barrier to 18x here.
IIRC it might be needing a second waiver for jump school.
What contract code are you going to MEPS with?

Some other possible variables are
1 - Your recruiter doesn't want to do the extra paperwork for jump school or 18x
2 - There may not have been 18x contracts immediately available in the system when you did your enlistment paperwork, as the 18x pipeline is often pushed out more than 11B OSUT.
Your recruiter would need to call the Rock and have an 18x date released for you.
He may not know this, or he may not want the hassle.
3 - You've already been dropped from one contract, they may be just trying to ship you as quick as possible, maybe you're a flight risk. :P

Give me a little more info, and I might be able to dial this answer in.

To answer your second question, your initial contract length has little bearing on your 18 packet. If you are selected at SFAS, you are required to sign an extra 4 years from memory? I think I have this a little turned around, but the principle's likely correct.
The Green Monster asks you for extra time when they want it, you're remaining TIS is of little concern.
But be aware things change, my memory is fuzzy, and I am far from a 79-Romeo gawd.

More info please.

S