For childeren most embassies don't ask for extra 500K, for spouse normally they ask, your statement that according the law any number of dependant can use the 500K is just wron, according to the law for every applicant regardless whiich of the 3 types needs 500K. This can be with a sponsor letter.
if you did your first report before day 90, your second has to be done before 180 and can be online, so better not before 90 in case you want to stay till day 180.
online works for people who have a stay longer than 180 days, so for DTV with in country extension, or for non-o who can extend there inititial stay for many times.
These situations are completely different from OP, which is travelling frequently and never stay long. No need for visa exemption back to back like your husband. Of course it is possible to meet an IO with a bad day, but that is possible with any visa. Your colleague did a border bounce, so was clearly tricking the system.
I think still a lot of countries give affidavit, and I know you did not ask questions, it is just a reaction your info is incomplete which might give the OP the wrong impression.