you don't know much about this since you ask that question. it's the eldest daughter that takes care of her parents when they are old it's not the son. When the daughter gets married the parents loose a future provider. SinSot is compensation for that.
not wrong dates - read the comments and read properly what is written in your visa. The valid from is the earliest you can enter Thailand and valid until is the last day you can enter Thailand and it also says for how long you can stay in Thailand
he has a visa and will not get a visa when he arrives. A visa is an entry permit and when it is shown in the airport it will now be a permission to stay
immi in Udon Thani don't ask for tm30 - they just check it online. 3 times I've got a proof of residence without a copy of my tm30. But of course a very good idea in general to bring it.