Check into what Cancer patients have to do. The doctors want them to eat
fatty foods because they lose weight superfast. This means homo milk, etc.

So you said your dad likes chocolate syrup with milk. Ok, so go to baskin
robbins and buy him a milkshake with 2% or homo milk that uses a nice
chocolately icecream (I love chocolate mousse royale from there but it has
chocolate chips which might be a pain in a straw so pick a different
chocolate). I'm actually experiencing a chocolate craving right now so I
might run out and buy a bar of dark chocolate (I don't buy milk chocolate
anymore, got used to dark which is mostly cocoa solids anyways). Buy some
chocolate milks in a bottle from Hershey etc at the supermarket.

Grilled cheese sandwiches on white bread.. a couple months ago I tried
making an old 1950s recipe for macaroni and cheese which involved the use
of bread and eggs, along with cheese and macaroni. It was rather
interesting and very fluffy. I could dig the recipe for that up it was in
my better homes and gardens cookbook from the classic recipes section.

None of the above is paleo, but your dad is seriously sick and from what
I've seen, paleo isn't conductive to weightgain so normal rules don't apply
here. He wants high calorie stuff and his personal preferences may be that
he's subconsciously aware of it.

Oh, and if you buy ground meat for him don't buy lean either, get medium or
higher. And of course, have him eat berries and vegs and stuff now and
then, might want to steam the spinach or whatever till it's all soft and
mushy so it's easy to spoon in. Walnuts are fattening too, so if he still
has teeth, a big bag of walnuts will be nice too.

I hope noone freaks out about what I just said.

Best,
P.