Re: Easing the Mainsheet
It looks to me like you are probably over trimmed for a beam reach. The sail almost appears to be on center. It's hard to judge from the angle of the photo, I'm basing it on the angle of the topping lift vs the angle of the backstay.
Since you don't have any tells on the main you'll need to use the "when it doubt let it out" method of trimming the main. Let out the main until it luffs, then bring it back in until the luffing just stops.
Why is the jib rolled up?
1986 Pearson 28-2 "Elena"