Hi rucan,
Congrats on passing the theory part. A lot of people get very nervous about that too!
You say you're scared to drive on the highway - if that's really the case it's probably too soon to contemplate taking the test. Confidence will only come with lots of practice.
I appreciate that professional lessons are expensive, but if you've mastered the basics of controlling the vehicle, and understand the 'rules of the road', is there anyone who would accompany you while you get more experience?
As to the test itself, I really can't imagine any examiner being 'lenient' - whatever one's age.
If it's any consolation, I stalled on the hill start, and later took a wrong turn on the test, but still passed. The examiner explained that the crucial thing was not the fact that I made a mistake, but that I didn't panic, and did the right thing to correct the situation.
Hope you can get lots of practice, and good luck!