So I FIMed this plant 2 weeks before putting it into flower, in this picture it's about a week and a half into flower. Should I remove the fan leaves that are sitting at the top? Would it increase my yield or would it hurt the yield?
Removing the fan leaves could stress the plant and stunt it a little but it is covering the lower buds... If possible you could tie them very loosely and bend them away so they are still getting light but aren't shading the buds, make sure to check often as you will want to adjust the string as the plant stretches
never remove a leaf unless you had an idea long before that leaf formed. There is a technique called defoliation. Nothing I have ever read on the internet is true IMHO. Defoliation is for when you have plenty of pot and plenty of time and plenty of room. And even in that teqhniqe we never remove the top fan leaves. And all the defoliation is done long before flowering. But if for some stupid reason you want to remove a leaf because you think it is blocking light or sucking energy, at least only remove the leaf and not the stem. And never more than two per day. It doesn't look stressful, the leaves snip right off. But it is. Very stressful. That is why it is not a technique for anybody in a hurry.