Number 1 is incorrect because the phrase is 'twice as much as'. You can change the number and say 'three times as much as, ten times as much as', etc.
With number 2, you're using the comparative form of the adjective 'good', where 'ten times' is an adverbial phrase modifying the comparative adjective 'better'. Again, you could change that number such as 'three times better, a hundred times better', etc.
In regards to your pie example, your brother ate twice as many pies as you. (Hopefully, those are small pies!)
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