I would let if finish...all I see is white hairs, so not ripe, but weather you smoke it now or not is up to you since at best your only going to get a couple of bong hits.
The yellowing of the leaves is a normal part of the budding process you want your NPK, but you want the numbers higher in the PK range...you still need N, just not as much.
No, not screwed, just could have done better with a larger pot.....DO NOT EVEN THINK OF TRANSPLANTING AT THIS STAGE!!!! your gonna have to water a bit more because of the small pot size...but I got to tell ya, you did great! for the size of the pot...really great....The plant will finish in it's...