Since that is a French design that never made it past Europe (this is a US based forum)... I'm not familiar with it, but likely the same as a 17 or 21 as far as boards go. There has to be springs to push the boards down. Possibly worn or broken? Check the http://hobie-cat.net
website for possible parts and assembly drawings of the boat.
Trampolines do add to over-all frame stiffness.
Rudder FAQ: http://www.hobiecat.com/forums/viewtopic.php?f=18&t=467
The French boats use the same rudder cam system.
A 16 rig is loose until the jib is hoisted and tensioned. Your rig should be snug at all times.
Boom: Should have a pin out the front of the boom... connected to a "U" shaped "Vertex" which then pins to the fitting (gooseneck) on the mast.
Mast rake varies by model and conditions. You can only rake aft to the point that the sheets still work.