Sorry for my English guys but I speak little little English.

If i open from SB 3x, 0.5bb is dead money and my FE is 2.5/4 = 62.5%

if i open from SB 2x, 0.5bb is dead money and my FE is 1.5/3 = 50%

Why ''field'' open 3x? if u open 3x or 2x BB have in any case pot odds for call with anythink, obv the problem is the reverse card imho.

Than if i open 2x BB must defence (m.d.f) not 38.5% but 50% 11.5% gap is a lot!

In basic for exploiting if villain open 2x from sb (Fe% 50%) range 60% (for random example)

my defence is: x= (50x60)/100 = 30% ---- 60 * 30% = 18% ----- 60-18= 42%

because when he fold from Sb i keep dead money and are a lot of money....

Is correct open from Sb 2x?? 

ty for comments :)