For 5d, take moments about point B. You'll get an equation involving W, l, sin(theta) and cos(theta). Cancel out as many terms as you can, then rearrange into the form then use the fact that .
For 6, you could probably take moments about the end of the ladder that's touching the wall. Use the value of F that you calculated, and an unknown position for the person on the ladder, and make clockwise moments equal anticlockwise moments, and solve to find the position of the person on the ladder.
(by the way I haven't verified the calculations you've already done)