I start with the colt and in my loadout.gsc I have it as colt, and its the switch weapon and laststand weapon, but when I buy the box and take a gun I just trade out the colt for that gun and can only have one weapon, the only way for me to get 2 weapons is to buy a wall weapon first

Sounds like one of the inventory size checks in _zombiemode_weapons isn't working or doesn't exist. Try coping your current weapons includes & delete your custom _zombiemode_weapons.gsc. Then paste the weapon includes into a stock _zombiemode_weapons.gsc.