1-2. For shame deny that thou bear'st love to any, / Who for thyself art so unprovident.: i.e., since you have so little love for yourself that you don't provide for your future, out of pure shame you ought to admit that you love no one at all.

6. stick'st not: don't hesitate. conspire: make evil plans.

7. Seeking that beauteous roof to ruinate: i.e., trying to ruin your own family heritage.  —I take it that "roof" is metonymy for "house" in the sense of "family," as in "the house of Windsor."

8. repair: keep in repair.

9. thought: attitude. mind: opinion (of you).

11. presence: appearance and manners.

12. Make thee another self: i.e., father a child.