1. He is a good deal stronger than Sam.
2. He is lots stronger than Sam.
3. He is far and away stronger than Sam.
...............................
Are they all grammatical?
yes, but I've never heard, nor would I say #3
That phrase is usually reserved for nouns with superlative adjectives, as in your other example.
Such as ... far and away
the tallest mountain
the best student
the unluckiest man on earth