There's more to saddle fore/aft than what you can compensate for with a stem, i.e., your hip positioning relative to the bottom bracket. You may have given up the most efficient angle for your legs, along with the rather useful pedals.
You could find a low stack shoe and pedal combo and mount the cleats further back into more of an endurance position, and chuck some 650b wheels on instead.
The shortest clamp style stem (that is typically found on many modern road and MTB bikes) is 32mm. Some unusually designed stems you can buy can get it all the way down to zero.
And if that is not enough, you can take a 32mm stem and install it in reverse! I've experimented with large aft seat position on a road bike. I found that hip position against the BB is irrelevant after getting used to it for a few weeks. What is relevant is the hip angle against the torso. The bigger the angle, the better. Moving the saddle back reduces this angle but you can compensate for it by reducing stem length / reach.
I also experimented with varying stem lengths with regards to steering stability. I discovered that reducing stem length made steering lighter. Not necessarily twitchy. Twitchy was only initially but after a few days of getting used to it. It wasn't twitchy anymore and actually stable and the light steering was incredibly useful for making tight turns. I went as far as taking a 32 mm stem and installing it backwards (not flipped upside down but rotated backwards!). After a short time getting acquainted with it, it was stable to my surprise and even comfortable if you have large aft seat adjustment. The only problem with very close and low handlebar is the knees hitting the handlebar when standing on the pedals even if not pedaling! That problem can be dangerous so I don't recommend it unless your handlebar is high enough, impossible to hit with the knees if you stand.