Professional, full time, part time or any degree of running a Dojo, Dojang, kwoon or whatever does result in exposure to tort liability, and I am pleased that you have an insurance policy.
You made the following statement:
However, I am an amateur instructor (no regular fees) and must have a day job or they will cancel my policy. And yes, I have their response in writing
If I understand this correctly, they require you to have a day job so their risk may be assessed on the basis of limited exposure resulting from your having less students.
In determining whether in a given set of facts that the MA is or is not liable for negligence and in what percentage, the waiver can be useful in determing if there was a voluntary assumption of risk.
Although in Massachusetts the waiver is void as such, might not the response of the student, coupled with the questions generally asked in either applications of written inquiries given by the MA to the prospective student be useful.
On the otherhand insurance companies are multi-state generally and it is in their SOP to get this form signed.
Pre application forms ( interviews ) can be useful in determining the health, sophistication and background of the student.
When my office was in Natick a few years ago I worked out in a Kenpo dojo next door to my office for over three years. It was part of a small chain.
I can tell you that the MA sensei were made very aware of the dictates of the insurance companies and possible acts which could constitute negliegence.
The loss of such insurance or the implementation of high surcharge fees can be a lethal blow.
I think, that in the long run, it was benficial to students in that mats, safety floors and equipment coupled with no sparring without full gear.
However it diluted the training that one gets from sparring with minimum gear (say gloves and foot pads only)without the blind side effect of full head gear (except for HighGear).
It was also my understanding that claims were few in comparison with the amount of students taught, but if anyone can tell you more about this on a practical basis, it would be GEM, sensei.