In the simulationsettings (the first step) you set the number of simulation to 30 frames and the draping to 15. The endpose of the simulation is on frame 30.  So in your simulation you have first 15 frames of draping and then 30 frames (0-30) frames of simulation. You don't have to set self collision for the canvas chair and also for the beach chair, unless you fold it.

collide with is only the frame part of the chair and the person who is sitting in it, and for the beach chair only the front- and back support .

You can run multiple simulations, but you can only do that one by one, first do the  chair and then the clothing. I don't know if svdl's stockings have a lot of polygons, but I've noticed that if a dynamic cloth has a lot of polygons (and vertices), the simulation doesn't work, the cloth of the the dress or pants or stockings go through the cloth of the seat.

regards,

Bopperthijs.

-How can you improve things when you don't make mistakes?