Why is it के instead of का? I don't see a postposition following "father," and I can't think of another reason for having it be oblique.
The plural form is used for respect also, many sentences that talk about someone's father or uncle, etc. will use the plural form, simply because they are your elder and you wish to show respect.
Is गरम the same as "garam" in "garam masala"?
Garam masala means that
It is a spicy one ,spicy can also said as hot so i think both are same
पिताजी should also be accepted