Should brake fluid come out of a misaligned disc caliper piston?
That is normal behaviour. You pushed the piston way out, so oil from behind it found a way out.

General actions suitable for your case as well:


remove wheel
remove pads
carefully push the lever a couple of times in order for the pistons to extend a couple of mms. if one is stuck, make sure you push the other one with a plastic tyre lever while pulling the brake lever in order to make the sticky piston extend.
clean sides of piston with earbud with alcohol. clean again with paper. this ensures free movement of pistons later on.
carefully fully push pistons back into their place with a plastic tyre lever. this is called "reset".
insert shimano yellow block
do a full bleed
remove block
install pads
install wheel
go ride


Also, make sure that no oil was spiled on pads or disk. If so, replace pads and clean disk very well.