I'll go with you on point #2 from the standpoint that bureaucrats typically and traditionally underreport and underestimate long term costs - you'd think that executives would get a clue about that, but no, they don't.
But I'll flat out tell you that Romney prides himself on being a "numbers" man. He'll stand up and quote chapter and verse on small points relating to any particular policy or legislation and do so quite elegantly - it's clear he does a certain amount of homework.
So why, pray tell, did Romney fail so badly in both failing to predict the underestimates for cost and the ultimate unsustainability of RomneyCare if he's such a "numbers" guy?
Romney cut spending in Massachusetts, a state that faced a $3 billion budget deficit. As a Governor, Romney did increase fees, local commercial taxes, and he also created an online sales tax. However, Romney also expanded a 2003 tax cut on investment, he created a New Market Tax Credit, and he stopped further tax increases. Furthermore, Romney saw the addition of 80,000 jobs during his time as governor. He held spending increases to 2.2%, when, according to the club for growth, spending should have seen a 3% increase during his time as governor given the population. His record as governor is very good in general, but outstanding considering the political climate he governed in.