Jos' anxiety about the end of the tunnel got me thinking: he was on the track when Wendlinger had his horrific accident right there during training in '94, wasn't he?

Well, yes, but it's not unusual for racing drivers to be uncomfortable when other people are driving.

What Max was actually saying in the tunnel was how fast he would go in his F1 car, and where he would brake.

I found an actual transcript, translated to English (and video with the original sound, instead of having it turned down):

00:01 Max: Do I have to put the seatbelt on? CameraMan: I would put it on
00:07 Max: Nice isn't it! 17years old, can't drive on the road but here in Moncaco you can!
00:15 Jos: Well Max, we're going to do a lap of Monaco. You're going to tell us how you're going to do it.
00:25 Jos:It's quite weird to get driving lessons from your son!
00:28 Jos:Are you going to keep the car in one piece?
00:30 Max: Yeah no problem
00:33 Jos: Jezus Max! ehhh Fuck!
00:40 Max: There is a bump here so you need to go around it.
00:42 Jos:It's not fun at all to drive along with him to be honest.
00:45 Max: Come of the brakes here, back on the throttle, as close as you can get to the wall.brake as late as you can.
00:53 Jos: Everything ok with Olav in the back? (dutch comentator)
00:58 Max: Try to get some curb here and get a good exit out of here.
01:06 Jos: This is were we enter the tunnel, how fast do you drive here with a F1 car? Max: At the end of the straight around 290kph.
01:16 Jos:Where do you brake? Max: at the 120m mark, but we're not going to do that in this car because I have to safe the brakes a little bit.
01:29 Jos: I don't like this at all!
01:34 Max: This is where you can safe a lot of time towards the chicane and that one is almost full throtle.
01:46 Jos: I'm so glad the lap is almost done! Oh jezus.
02:01 Max: Get a good exit onto the straight.
02:08 Jos: Ok just slow it down now, I'm done with this after one lap.
02:14 Max: What? It went alright didn't it? Jos: Yeah, it looked alright. Olav: HolyMoly!