Please stop. It sounds like you are compounding errors.
Don't panic, as CA glue can be broken.
It sounds like you have something wrong with your ruler, or if you are converting to metric your formula is out.
It seems like somethings are one inch out.
All the measurements on the plan worked for me. But not always first time.
You can see from the plan where the foot for the main mast should be. Roughly mark this out with a pencil.
Then measure from where it should be to the stern (on the boat not from the plan).
Compare this measurement with that on the plan. Sometimes if I do this and/or compare the difference a penny will drop.
Did you measure the mast footings and compare with the beams first? These could be out.
I found the measurements on the plan a bit odd, but if I dry assembled 3 or 4 times first (then slept on it) the measurements made sense.
You may have to break off a few bits and re-glue.
Worst case the beams are out. But they can be re-glued onto a bigger gusset and some filler added.
If you are using a steel tape, then also go out and buy a steel rule (or two). B&Q do a nice range and one of the 24" rullers has a good conversion table on the back, usefull for choosing drill bits.
BTW the drill bit sizes quoted are not critical. Just go for nearest metric.
So again, go back to the drawings, and try to see where the original error lies.
Good Luck.