Why would he be paying child support?
Look, PF was concocting a story and part of that story was to use words like "exchange the baby" and "pay for child support" to support his tall tale that he and KB had separated. PF also told people he was given custody of his child, that he and KB were no longer together, that KB had abandoned the child in the hospital, had disappeared before only to be found weeks later at a substance abuse clinic and that she was an alcoholic. I believe they had combined their finances and that included providing for their child, car insurance and phone plans. I share those finances with my husband, some people share those finances when they are in any committed long term relationship.
I also believe they postponed the wedding due to finances. Some couples do that to accommodate family and a nice honeymoon. Weddings can be pricey when you have to pay for family from out of state to stay in hotels and be fed.
We can also be sure that the relationship between SF and KB wasn't good. So I'd be inclined to think anything SF said about KB and PF's finances and relationship would be to paint KB in a bad light or make it appear that the two were broken up.
Fact is, there was no custody agreement, so using words like "child support" doesn't make any sense unless PF and SF were trying to manipulate people's opinions by using specific language.