FE250 / 450 learning

I doubt you'd notice much of a difference with a 250 in pivot turns, weight difference is negligible and low-rpm power is less

i predict it will click suddenly and be a factor of butt position, throttle and clutch control, and decisiveness

and pushing down the front and release to get the spring to help

i don't know how to wheelie properly - i do it more by accident than on purpose :/ i think i'm too hesitant

have you seen the enduro and trials cross training videos on youtube?: CROSS TRAINING ENDURO SKILLS

To get the front to lift is a combination of things to happen systematically.
Good to have a slight up hill and a rock or something to start bouncing the front up to start with and tractable ground.
Start heading up toward the small rock or other item that will help compress or bounce the front end up some , head up toward it as you let the throttle off quickly , you time it with practice , so the throttle as it is backed off your weight goes forward compresses the forks , the rpm as you hit the small rock will be just above idol ,then lean back at the same time you roll a little throttle on it, or slightly pop the clutch with smaller revs. Wait until you have all your maximum body weight over the rear of the bike and the rear end is compressed first with arms stretched out. What you are trying to achieve is maximum traction and body weight on the rear wheel without spin and the engine rpm torqueing , it is easier to control this way when learning. Also a low gearing may help to start with.
I like to keep weight on your back side toward the rear of the seat/rear guard to get it up, as the bike pivots up , keep your torso vertical so you maintain balance and control of the bike.
After some practice of balance, throttle control and weight distribution on the bike and some crashing out , you then add the turning into it.

To turn the bike on the back wheel, during the above mentioned process of lifting the front up , just lay the bike slightly over off centre, as the front comes up you can drop the inside leg off the peg , the leg will act as a counter weight and support the bike , once the bike is just before flipping over, may need to fan the clutch slightly to stop stalling and maintain balance and drive in the back wheel , some of your body weight transfers to the leg whilst holding the bike up. The bike will just pivot around with practice, timing and body position.
It will require lots of practice and energy , but once mastered, requires very little energy and effort to pivot and turn a bike on the back wheel. It is a pretty hard thing to explain exactly on paper, practice is the key to mastering it.

Hope that helps some to get you started.