How would ATC try to establish contact with a VFR craft?
Long story short, ATC has no reason to contact you but if they were to try they'd probably use 121.5 (see below). You're not in their airspace and the whole purpose of that airspace is to ensure separation, so as long as you remain clear of it they won't be concerned about you although they'll probably report your position to the 747.

As for your specific questions:


That's your decision as PIC and no one else can make it. But I wouldn't spend much time in a zone where I'm at high risk of a wake turbulence encounter.
No, there is no requirement for you to be in contact with ATC in that airspace so you're not wrong. It would be good to get flight following if possible, but that's optional and might not be available anyway.
It's hard to say what "too close" means and it could change depending on the time of day, if you're thinking about traffic. Again, this is something that you as PIC have to determine.
They won't try to contact you since you're outside the class B and they have no reliable way to contact you anyway. And considering wake turbulence again, "too close for their comfort" is probably more like too close for your comfort :-) Aircraft size isn't a consideration for right of way (see 14 CFR 91.113).
They won't for the reasons above. And they also can't know if you have a working radio, which frequency you're on etc. But they would probably try 121.5 because a current FDC NOTAM states that you should be monitoring it if you can:



  ALL AIRCRAFT OPERATING IN UNITED STATES NATIONAL AIRSPACE, IF CAPABLE,
  SHALL MAINTAIN A LISTENING WATCH ON VHF GUARD 121.5 OR UHF 243.0.


The AIM also suggests and encourages all pilots to monitor it (e.g. section 6-2-4).


It's hard to say, the FAA's ATC instructions don't cover this situation (or I couldn't find it). But giving a specific bearing is unlikely (a bearing from what?) because you might not have the equipment to verify it so perhaps "12 miles north of DFW at 1500ft" would be more likely for the position part.


Of course, if ATC really, desperately, urgently needs to contact you - like if you fly straight through the class B without a clearance - then they can always request an interception. That would really ruin your day, so monitoring 121.5 if you can is probably a good idea.