narita to osaka, arriving late

hello, let me explain my predicament. i will keep it short so it is easy to read and understand:
-arriving in a few weeks at Narita Airport Terminal 2 at 6.45PM
-Must go to Osaka ASAP
-Has a JR PASS (ALL)

I understand that in my case, i HAVE to make the 2003 shinkansen from tokyo, but is there any other way of making it to osaka?

i think i will have to take one of the JR buses from tokyo station..

also, if i decide to use the nozomi shinkansen whilst using my JR PASS, do i just pay an extra fee? or must it be the whole fare?

It is impossible to catch the 20:03 shinkansen if you arrive at 18:45.

Indeed, you could take a JR overnight bus, but that could be a waste of your Japan Rail Pass (depending on the rest of your program). Here are the details about the various JR buses:
http://www.jrbuskanto.co.jp/bus_route_e/#list08

aftech,

If you really have to get to Osaka at whatever cost, and know where and how to buy tickets on the spot quickly, your last train from Narita T2 appears to be the 2013 Keisei Skyliner to Ueno (much, much faster than the JR Narita Express). You can then catch the Nozomi 269 from Tokyo, which arrives in Shin-Osaka at 2345. That will set you back 15,000 yen or so, as none of that is covered by the Japan Rail Pass (except for Ueno to Tokyo on the Yamanote Line).

if i decide to use the nozomi shinkansen whilst using my JR PASS, do i just pay an extra fee? or must it be the whole fare?

You have to pay the entire fare, as the Japan Rail Pass is not valid.

Using Keisei, You get off at Nippori, not Ueno Station.
You can transfer to Yamanote-line directly at Nippori.

alright thanks for that then guys, i think ill just use the overnight buses. So the JR kanto buses are free with the JR pass? i just book the buses at the same place i book the shinkansen tickets?

I am not sure whether the premium buses are covered, but all the other JR buses along the Tokyo-Osaka route are. Seat reservations can be made at the ticket counters of JR stations, but if you travel on a busy day (e.g. Friday evening), I recommend to make reservations in advance by phone. See the above linked official website for phone numbers.