2. thy sight: the sight of you.

3. Mine eye my heart thy picture's sight would bar, / My heart mine eye the freedom of that right: My eye would [if it could] prevent my heart from seeing your image, [and] my heart [would deny] my eye the freedom to claim a right to you.

5. him: the heart.

6. closet: private room.  crystal eyes: i.e., clear-sighted eyes.

8. in him: i.e., in the poet's eyes.

9-10. 'cide: decide.  impanneled / A quest of thoughts: impaneled a jury of thoughts.  all tenants to the heart: —Since all the thoughts have the heart as landlord, the "jury of thoughts" might be a bit prejudiced.

12. moiety: portion.