hmm I feel your pain, I would like to do more endurance training.
I tell myself I will do weights for a couple years to build up strength, learn technique and hopefully injury proof myself.
Then when I live somewhere more sunny and have money to spend on nice bikes etc will get back into endurance stuff (I have complete an IronMan and Comrades Ultra Marathon on my bucket list).
When I was doing 5x5 I found the gap between 5x5 and 1RM too big. For me any squat over 100kg feels totally different to 5 at 85kg.
That is the advantage that other programs have over a 5x5, you can do heavy singles, doubles, triples etc.
5/3/1 is cool if you like spreadsheets and the like, but is not the only solution by far, you are a unique snow flake and need a training program that matches your needs.
Do you know
you are eating enough? You might think you are, but you might not be. Eat like crazy for a month and see what happens? Might unleash the giant within.
Also your not weak by a long shot, is this just fishing for compliments?
Reality check, you are the 2nd strongest cyclist on the Olympic table http://www.veganfitness.net/forum/viewtopic.php?t=20394
the other "strength" table is irrelevant but you are in the top 2/3.
Last thing, when last did you have someone slapping or shouting at you when you are training?