Brave your getting utterly confused lol.
That video was to show how good the Inverto ultra black lnb is as regard pulling in teh best strength via AGC.
As i would never able to do this with other lnb's, soon as mine would go round the 50% it would lose signal, glitch etc.
The video was no a means to say this is how your snr should be
Once i took video i set the dish to max snr i could getin order to get tip top signal as i would have not left it at the percentage i had in the video as it was a demo for others to show them the quality of the new lnb.
My snr i got max on motorised is round the 70-80% and even on foreign i get 90's.
Your issue lies in the dish you are sharing for sure bud.
Is there no way you can replace the dish yourself as they only £20-25, could be an older dish and lnb, maybe dish loose depending where it is located.
Maybe loose cabling from lnb to junction box or whatever is be used in order to split the signal how many ways.
Can you take pic of your dish aslong as it is not on top of a tower block which in that case you could ask caretaker if he can open door to get to the roof.
After all it will benefit everyone and mostly you.
I am sure there are other knowledgable people here whom can explain in greater details how it works, but all my information is from me learning little bits here and there and doing some stuff my self as i am in this field no expert.