I have some issues with my transmission. 2006 with ~53000 miles on it. OEM synthetic fluid. OEM everything engine/drivetrain

1.) Stiff shifting going into the 2nd and 3rd randomly - doesn't grind, just stiff. not a consistent thing but I'd say 75%. sometimes goes away when transmission gets up to temp.

2.) Leaks from the clutch breather slot at the bottom of the transmission and some appears to be coming out of the slave cylinder boot area. This started either before or after I got my Clutch Slave cylinder replaced by the dealer about 3 months ago. I told them the transmission was leaking oil (clutch res wasn't low) and they (Honda dealer) ended up replacing the slave cylinder. note that shifting was not bad and the clutch wasn't going to floor. For some reason the leak went away and it came back about a month ago and then went away again.

more background:
- Transmission oil was WAY overfilled by dealer - Last Saturday I put the car up on jack stands, got it somewhat level and slanted a little to the rear, opened the FILL hole on the transmission and oil came GUSHING out (like you were pooring oil our of a bottle). I quickly plugged the hole before too much more came out. I double checked if the car was level, I put the rear up a notch so now the car is slightly leaning towards the front, unplugged the hole again and STILL there is oil coming out fairly quickly.

Will an overfill on transmission oil blow out some seals?
Will an overfill cause the transmission to have stiff, inconsistent shifts?
will an overfill cause anything to get damaged?

about the shift quality, I haven't tried bleeding the slave cylinder again yet so I know that might be a part of it. I think I will leave that up to the dealer though.

The car has a CPO warranty and also extra mechanical warranty on top of that. I mainly need to know what could have happened and what is wrong so when I go talk to the dealer, they can't jerk me around and this will get fixed asap.

Thanks!