I have found several errors as well with the English subtitles.
Sometimes, what is said is wrong (like when Ennis is leaving the Twist farm at the end, and he is outside holding the shirts in the bag - the subtitles have him saying, "Thank you, M'am," but what he really says is "Thank you for this." That's a HUGE difference to me.
Other times, who says what is wrong. Like in TS2, the subtitles make it look like it is Ennis who says "I'm sorry," which leads us to believe that Ennis is possibly sorry for having taken off in the morning without so much as a goodbye to poor Jack, when, really, the "I'm Sorry" line is uttered by Jack because, as I interpret it, he is sorry for having "pushed" Ennis into kissing him. (Jack was always afraid to scare poor Ennis off and was always careful about what he said and didn't say or how he approached him, etc.)...
As for the conflicting reports of what is being heard and said, I have not yet heard the "F _ _ _ _ _ " by Jack in TS1, but will look for it. I HAVE heard the "I Love You" in the shirt scene at the end. I don't necessarily want to hear it because I believe we all know exactly how Jack and Ennis feel about each other and why each of them has never really said it to the other over the years, but I do see and hear Ennis breathe that "I Love You" into the shirts as he exhales.