I interpret the reference to mean you have to meet (i) & (ii) and either (iii) or (iv). However, some interpret it to mean (i) or (ii) or (iii) or (iv) must be met. Based on my interpretation because the task orders are cost type and not firm fixed price, they are non-compliant.
This is a great question. Your interpretation is the closest but not quite correct.
The head of the agency must determine that (i), (ii)*, AND (iii) are all affirmative OR that (iv) is affirmative.
* note: to meet condition (ii) only (A) OR (B) has to be affirmative.
This is based on one of the canons of statutory construction “expressio unuius est exclusio alterius” (the inclusion of one is the exclusion of others); there is only an “or” after (iii).
You are correct that because yours are cost type orders; your only justification can now be (iv). See DFARS 216.504(c)(1)(ii)(D)(i) for guidance on who has the authority to make the determination for you should you seek it out.