You seem to have a misunderstanding about how these FFPs work. You can only redeem AAdvantage miles through AA. You cannot redeem other oneworld frequent-flyer currencies via AA. You can, however, redeem AAdvantage miles through AA for award flights on AA's partner carriers, if and only if those partners are making award flights available to AA.

Here's an example of an Iberia award flight for two passengers in Economy being made available to AA for redemption with AAdvantage miles:



If aa.com is not displaying Iberia award flights on the dates you want and in the class of service you want, it means that Iberia is not making such seats available for redemption with AAdvantage miles. Iberia might or might not have seats available for redemption with IB Avios at Iberia's website, or with BA Avios at ba.com. And just as you cannot redeem Avios at aa.com, you cannot redeem AAdvantage miles on the BA or IB websites.

If you decide that you are going to pay cash for two Premium Economy roundtrips, you might consider applying for another credit card with a lucrative sign-up bonus. The cost of those two tickets would go a long way toward meeting the minimum-spend requirement for such a bonus. The only caveat is that by the time you received the new card, the price of the tickets might have increased.