Yes it can do damage, if moved too far and valve and piston have a fight.
You would be best off using a dial gauge to find the true TDC, this will be the centre of the each way sway, that exists before the needle starts to move again, typically a span of 4-6 degrees, so find the true centre, do this also on the cam LOBE not retainer, centre again as above, then fit degree disc, on crank turn crank to 118 degrees after tdc, with the full valve lift dial still in centre.
It will help if you have a nut welded to the cam(thrust) locking plate if you can, simple then to just wind a bolt in to touch the cam at an angle to hold in position while you fit pulleys etc, tension belt before fully tightening vernier clamps.
tabetha