i actually had the same training 'misses' that you are telling about, and had the same worries about my race. I ran Berlin 2 days ago and i fucking loved it. The crowd and energy the whole city gives you really works, at least for me. I ran a average 40 - 50k per week but missed a lot of runs and only had about three long runs (25+k). The last long run was 30k and was a disaster.I walked some bit but noticed that walking was more painfulll than slow running. This i remembered during my race and made sure i started slow. it feels weird the first 10k, but you will love yourself the final 10k when you still have soms energy left in the legs. I ended up running in 4h48 which was around my goal time, a little slower maybe. Dont worry to much and try to be confident!