No. Yes.
Depends. Can you give us some info on the brew and what your intentions are?
Based upon your recipe, no, sugar would just dry and thin the beer out. If your efficiency falls short and you want to boost it back up you can add DME to account for the inefficiency of your mash. generally 1lb will raise you 10 points.
You can take a pre-boil gravity reading which should fall about 7-10 points below your expected OG post boil.
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