I am currently reviewing and redesigning the electrical installation of my property which came with a 100A SquareD QOD6S MLO load center very badly abused and about 130' away from the service drop which is a single phase 120V. There are plenty of problems in this circuit and one is this center being the only (malfunctioning) station between appliances and the incoming feed. I need to rewire this as a sub panel and install a main disconnect at my properties entrance. I am a layman in electrical installations, I've had my share, but rewiring the whole circuit is a step up in my history. I am aware that this is dangerous and will therefore call the provider to have them cut the service before pulling/installing anything.
My confusion is about the fact that most articles written today call for 100A or 200A main panels/disconnects to provide the necessary load, which I understand, but applies mostly to directly connected main panels. I hardly read anything about spread out configurations where the service drop is way separated (like my 130') from the living space. There are some but not enough.
My power company (Mexican national power) has its specifications for the basic installation (totally ignored on my property, probably due to dating) which is the following (translated and redrawn original illustration with comments in italic font): So here's my doubt:
I redesigned the existing panel to become a sub panel of 100A (we don't have a lot of continuous draw). Its breakers will add up this much (4x15A & 2x20A). The underground wire run from the panel to the property entrance is #8 or #6, cannot figure anything out because it has no marking at all, so that would be rated somewhere between 40A and 75A depending on the insulation. Now the power company recommends a main disconnect of 30A connected to the meter with THW#8 which is rated 50A.
How do these numbers add up in reality?
Or in other words if my continuous load was greater than 30A how would a main disconnect of that size not trip that?
I read this answer to another question where it's said that
Don't bother trying to coordinate the trip rating of this "shutoff switch" breaker with the actual supply breaker in the main panel. That must be sized to protect the wire to the subpanel.
Can I be fine with a 30A breaker as a main disconnect for a 100A sub panel 130' feet away?
If yes then why so?