for actuators you best bet is the gimson range http://www.gimsonrobotics.co.uk/

but i used a car seat actuator in scruffy and it can lift about 24kg but there not the fastest actuators
if you know the actuator lifting capacity then and where the actuator connects to the lifter , on your drawing it looked about half way between hinge and wedge then you would divide the actuators lifting capacity by 2, and if it were 1/3 away from the hinge you would divide by 3......

as far as im aware its im correct but someone please correct me if im wrong