An AVR will attempt to correct the voltage to be the correct 120/240 when the load varies and the tractors governor hasn't corrected.
Depending on who has built it from what I recall it will correct the voltage from around 56 Hz to 62 Hz, I don't know why those numbers stick
in my mind it would seem to me that it should be able to trim on both sides the same amount which would be 56 Hz to 64 Hz.
As far as the length of the pto shaft any shaft bought should be fitted to the tractor and application;
in this it would depend on the method of mounting the generator.
If the generator is pad mounted and you back up to to connect to it, it could be everwhere from very short to fully extended.
A trailer mounted unit will depend on the trailer design and tongue length.
A 3 point has to be connected to the tractor or be carefully backed to for the pto to be the proper length.
I prefer a trailer mount for several reasons;
I can tow the generator with most anything, atv/utv, truck, car, or tractor to were I want too.
Any tractor can be easily connected to it with no concern of 3 point sizing or category.
It is much simpler to connect to when it is needed, just back up to it and connect the pto.
Often I do not even bother putting the hitch pin in the drawbar when using mine,
I leave it parked in a convenient location with the tongue jack down and the tires securely chocked.
The reason you are not getting many comments on your announced method of connecting for powering the house
is that it is not a proper or desirable or safe method of doing so.