I am also kinda scared with my last few weeks of Half marathon, the last weeks including the following long runs:
4 to go: 13miles
3 to go: 13 miles
2 to go: 14 miles
1 to go: flat out 10k
It is my opinion that i will be too tired, but that's because I have started learning about how my old 39 year old body needs to res, so I will definitely change the schedule slightly.
Schedules are there to give us guidelines (unless you are a long athlete with a team to support you), but there are no schedules that fit everyone. If you feel like the final 2 weeks are going 2 be too strenous, chances are that you are right and you should modify it slightly...
This is my opinion tho, I'd wait for more well informed opinions from other ppl around...
Cheers! 
David