the most important technical thing you already achieved, you can make it consistently to map30! definitely this is frustrating as hell, I cannot imagine making an awesome time in doom2 in an D2 run and map30 ruins it... similar stuff (although not so much luck based, more skill based) happened to me with an AVJ.wad map32 run, there the most difficult part as you know very well is directly at the end and getting there usually takes >30 mins (in the past). dying there always made me to stop trying that run for ~2-3 days. nevertheless, after that period I always felt like trying again :). long story short: you are already able to consistently run the thing, if you will try it a few more times I am sure you will be able to do it. but if it angers you too much, make a break and wait till you have fun running it again. I would try to see the path as the goal, like if you enjoy running no matter if you will set up a record, then do it! if it is only fun if it works out, I think it is way too frustrating... for example: I like to run doom2 in D2 UV although I know I am nowhere near the world record (really, by far xD), but it is nevertheless fun for me trying it :)!