Credit utilization between 1% and 30% | Credit card reward programs | Discussion forum

Watching my Equifax, I have been able to acheieve a decent credit rating up from low 600s a couple of years ago.
Goal would be to get close to 800 in order to get the family a viable low-interest mortgage (mid-700s now).
I had a few questions that I'm hoping folks will be able to share their insight.

Question A)
I have recently been approved for a couple Credit Cards that now gives access to quite a bit of credit.
From the reading a bunch of online resources, the consensus is to use your available credit, MORE THAN 0% every month.

There seems to be different opinions, however, on how much credit you should use:
>>>Some people say it's ok to use just 1% of your available credit
>>>Some people say you should use up to 30% of your available credit
>>>Some people say to use no more than 25% of your available credit

Question B)
The next question then relates to, is credit utilization based on a card per card basis, or is the score based on my TOTAL available credit, across all cards?
Reason for this question, is while we have access to many cards, we would like to use our preferred card that gives us access to flight reward points, and use all the other cards very little, if AT ALL.

Question C)
Another question in this mix, then relates to maximum credit limit per card:
If the right answer is to use 30% of available credit, but we have let's say for example, 3 credit cards with $20,000 limit each, does this mean that we should be using the 3 cards:
$20,000 x 3 cards = $60,000
30% of $60,000 = $18,000

Referring to Question "A", and using the "30%" line item, does this mean it is preferable to the credit bureau to spend $18,000 per month to gain credit rating? (whether it is over 1 card or many is referred to in Question "B").
This then brings up 2 questions that is also online, but I could not find clear answers:
>>>If the $18,000 is too much (not reasonable) to spend on a per month basis, should we contact the credit cards to reduce the credit limits on a per card basis?
>>>Many online resources say that if you have high credit limits, you should keep them as it takes a while / is hard to acquire credit from financial institutions > but in this scenario (using example above), $18,000 per month is not achievable.

Sorry for this lengthy multi-part post, these questions seem to be all related, and I don't think I can make the right choices without all of these pieces in place.
Thank you in advance for all of your valuable insight and answers...