I can address several of the last issues. You are NOT allowed to begin your trip without a properly mounted and operational ELD unit, and should it fail enroute it must be repaired or replaced at your DESTINATION. That is where the 8 days come in, while some otr drivers have cross country trips where it is 5-8 days to destination, our dispatches are generally less than a day. PHL-HRS, CLT-GAF, you name it, it is a destination, according to the law it must be repaired or replaced, no gray area. There are very few exceptions, the Companies failure to install and maintain ELD's is NOT a valid reason.
The dispatching of non-ELD vehicles comes down to US. If you or I hesitate to operate a non-compliant vehicle, fine you are well within your rights. As we all know there is always someone who, for whatever reason will say, "If that a$$hole won't do it I will, I don't care, I've got to go". Usually the same ones who never pre-trip, hook-up in 8 minutes out the gate, every terminal has one. How many times I have heard, "so and so doesn't have a problem with it", all I can say is do what you have to do, but verify and get a witness.
Search 49CFR, part 395, subpart b. Its all there
Stay safe
i know our ELD's "connect" to the engine (not even sure why) and "identify" with each particular tractor#.
Are ELD's even required to do this?