Strength of substituted Carbon Double Bonds and C-halo bonds
Out of the 2 bromo compounds, the first one has has stronger $\ce{C-Br}$ bond, because the lone pair of $\ce{Br}$ is in conjugation with $\ce{C=C}$. 
In first case I think Compound 1 is more stable for the reason that it has more substituted $\ce{C=C}$. In reasoning 2 I think when you think about decrease in bond order, the tendency of pulling electrons of $sp^2$ carbon has not decreased. Me- group itself donates electrons because Carbon is $sp^2$ hybridised. The tendency will not increase or decrease. I think it will remain in the form of slight polarisation.