Got a couple of situations that are similar, but I thought I would explain them both in case they are different. In both situations, it comes down to whether you select your target first, or the weapon. My opinion is that you would select your target first, then check range and arc, then select which weapon you are using from whichever ones are legal to use.

Situation 1:
I have Biggs and Wedge within 1 range of each other. My opponent has a Y-wing with an Ion Cannon. When measuring from the Ywing, Wedge is at Range 2 and Biggs is at Range 3. Can my opponent declear he is using his ion cannon and therefore target wedge, since biggs is at range 3. Or is he forced to target biggs, and then forced to use primary weapon since biggs is also out of range of the ion cannon.

Situation 2
Again I have wedge and biggs within range 1 of each other. My opponent has any ship that can take a missile, and a target lock on wedge. Can my opponent declear he is spendig his target lock to use his missile, firinig at wedge since he was the only one with a target lock on him and therefor the only legal target for the missile. OR, is he forced to target biggs first, and again, use hisprimary weapon since biiggs isn't wearing a target lock and therefore not a legal target for the missile

Any input on this would be much appriciated

This is covered in the FAQ:

Q: Does Biggs Darklighter’s pilot ability require
an attacker to use its primary weapon
against Biggs, even if the attacker could
use a secondary weapon against another
ship at Range 1 of Biggs?
A: Yes. If possible, the attacker must target Biggs
instead of any other ship at Range 1 of Biggs. If
the attacker has more than one weapon available, it
must use a weapon that can target Biggs.

Situation 1: If Biggs is in the firing arc of the primary weapon, Biggs must be targeted.

Situation 2: Again, Biggs must be targeted, regardless of the target lock.