Jeff scoured the Chronivac for options but didn't simply want to change his dad back, Mike would realize its been less than an hour and be upset, or worse, use the Chronivac to ensure Jeff couldn't interfere.
After a little research online, and in his biology textbook, Jeff thought the problem wasn't that Dad was inside of him, but that he wasn't helping in any way but could only possibly cause problems... The best case scenario is that Jeff is left unharmed. But that all changes significantly if he is helping somehow.
But how? Jeff cycled though hundreds of package options and when he was about to give up he fell upon something that seemed to be what he was looking for... kinda, the situation is a bit unique.
Jeff found the organ package, where one being can act like an organ of another. Jeff was able to select his dad's profile easily but then he needed to choose an organ for him to become or replace. Jeff really didn't want his dad replacing any of his vital organs, so when Jeff saw the option to create new, he selected it.
Jeff typed in that the parasite would grow into something that mimicked the function of an organ and when his dad was ready to leave Jeff's body, he would be a rice sized piece of organic matter that would find its way back to his intestine, like he was expecting. The new organ would stay performing its new functions.
As for the functions the organ performed, Jeff was initially unsure what to do. His body worked pretty good, he was 16 and aside from his single parent abandoning him for days to months, and being low in the schools social hierarchy, and homework, and having no idea what to do with his life after high school, everything was fine...