Daewoo Matiz experts please help: Crankshaft pulley bolt

[M4cruiser]

Hello all,
My daughter's Daewoo Matiz needs the water pump replaced, and it's behind the timing belt.

I've got as far as the crank pulley - and the bolt is tight!

Tried 3 methods:
(1) Reconnect battery, put socket (17mm) and breaker bar (2ft) in place and flick the starter. The breaker bar just stopped the engine when it hit the "end stop" (the concrete floor).

(2) Put wheels back on and lower to the floor, put it in 1st gear, handbrake on, and use the breaker bar/socket - strange but the engine kept turning (half a turn at least) and went all springy, and wheels tried to move a bit but didn't. I couldn't understand why, but didn't want to push it any further in case I broke something. What could be happening?

(3) Insert thick screwdriver up into slot under clutch area. This did lock the engine. but trying then to undo the bolt made the screwdriver bend and jump out. Again I thought I might break something if I pushed it, presumably the screwdriver is only on the flywheel teeth, which are not always very strong?

Can anyone assist please? I can't see if it's possible to change the water pump without removing the crank pulley but it looks impossible.

Thanks in advance.

[B'stard Child]

You need to be able to lock the flywheel (thro the starter motor hole typically) - I've knocked some makeshift tools up in the past but you need a welder in your tool kit

Or an impact gun sometimes cracks them free