I don't think they portray Jack as perfect. In 1x02 he was drinking and staying out late and in 1x07 he was too busy/tired to pay attention to what was going on with Rebecca and the kids.
I do feel for Rebecca in the present though, because it seems like even if he may not be perfect Jack was the fun dad whereas Rebecca had to be a little more strict. Also, since he died (maybe when he was quite young, we don't know yet) he gets to stay favorable in the kids' minds while they place any blame for their childhoods on Rebecca.
One thing is for sure...if they do get divorced because of Jack's drinking or cheating, the kids do not know about it at all.