Is less a form of adjective?

Answer 1

1. Yes, the irregular Comparative degree of the adjective "little".

2. A sort of suffix (a tool) used to form the Comparative of Inferiority of the longer adjectives: "a less interesting book" or of the longer adverbs: "He swam less rapidly than expected".

Answer 2

It can be either.

Used with a noun, it is an adjective: less money, less worry.

Used with an adjective, it is an adverb: less worried, less expensive

*although some of these could be considered 'negative comparative' compound adjectives.