It sounds like you just swaped bars & expected everything to work out like magic. The contact points are all in different places & your positioning is completly different between flats bars & drop bars.
Beings that nothing fits now, it's no wonder you are uncomfortable, unconfident, & unsure about the switch.
As far as handling: Have you ever taken a state approved motorcycle handling course? The technicals of bike handling skills are pretty independant of handle bar choice.
Bar style isn't the cause of your difficulties.
Edit:
It sounds like your stem is at least 2-3cm too short now. The hand numbness is the give away. Too much pressure because the bar is too close & the contact points are probably ~44cm apart & not the 66cm apart they would be on a flat bar which would have the effect of making it closer still.
Last edited by base2; 05-05-20 at 12:20 AM.