It sounds to me like your snake is just being a snake. I have some that typically show very little food response but occasionally they act as if they haven't eaten in years.
As far as the seperate feeding tub, you're right. It's been proven outdated and counterproductive.
- I've been feeding all my snakes inside their enclosures for years, and up until last week I had NEVER been struck at INSIDE the enclosure. (My Borneo STP struck the other day, but not during feeding time). The "cage aggression" has been proven to be nothing more than a myth.
That being said, if a seperate feeding tub has been working for you and your snake for a few years I don't see any harm in continuing to feed that way.
On the other hand, it couldn't hurt to start feeding inside the enclosure either. If he'll eat. It may be tough to transition him at this point, but as a well fed adult a few missed meals over a few weeks or months won't hurt if it takes a few tries to get him eating.
If you're interested in convincing your Dad that feeding tubs are old school and counter productive you could bring up some of the many threads on this forum that prove feeding tubs have basically gone obsolete. Present it almost like a school assignment. It may help him understand.