bloody hell, ouch! Private hospitals here are amazing just like in BKK but also treat you like a cash cow especially if you have insurance. Assuming she'll be in a private hospital in Thailand to give birth then it makes no sense to me unless it happens to be considerably cheaper in Thailand compared to the private ones here.
no noticeable differences between the private hospitals from my experience, certainly not Samitivej in BKK and FV in HCMC anyway. Not that I have experience of giving birth in either...
Either your husband gets a non-O based on being over 50 and you become his dependent or you get a tourist visa before entering Thailand which is good for 2 months, go down immigration and extend for 30 days then you leave.