As the batteries cool down, ideally charge rate should be reduced, the values listed by Victron are in line with most cell and battery suppliers.
You are right about the different boat scenarios, my NG batteries are on a boat, but I have more batteries vs typical use and a lower charging rate so one set is ideal. Yours is less easily covered.
One point I will note is that you will need to be at 14.0V to get your high recharge rates from the genset, the 13.7V setting only lets me charge at 0.2C max, which is fine because that is all I can do, but I rarely go below 70%.
I think for your number 1 and 2 you need something like 70% SOC threshold, 30 day interval and 2 hr absorption. When on shorepower you should never drop below 70% and you get once a month full charge. The same if moored off grid with good solar. If moored off grid with poor solar the 70% will kick in 14.0V charging ready for the generator kicking in. The 70% could be varied as long as the SOC threshold triggers before the generator starts.
Then in use, use the 70% threshold, 30 day interval and swap to 10 minute absorption. Then you get good charging rates most days but avoid too much absorption.
There will be some trial and error to get the best out of them.