What currency are we talking here? The average US $ price of yachtworld CS 36 T 79-81 is around 73k asking. Yours is 93K US and you need to spend 10K min depending on electronics and if there are other messes, which it sounds like, more.
If the broker says the min sale price for others is 75K is he talking CAN $? What year is he talking about and when did he sell it - like an 83 3 years ago would have been worth more. Nice guy or not he is selling and you are buying so a jaundiced view is appropriate.
If you are paying 90K Can then that is about 20% below asking which would be about right maybe, with some minor adjustment for faults, but not for electronics which you knew about. Even then it may be high.
But if you mean 90K US even as an asking price that seems high for a 1980 36' asking price not settling price.
Owners are often optimistic and will try it on. After many months on the market they may well be glad to get 2/3. But when they price more realistically at a bottom line you might still get 10% off.
The NADA value for what it is worth is way below this.