Hi Vikram,
I'm afraid you have identified a feature that is not yet present in SasView though we have had several requests and it is "in the queue" of tickets for feature requests. Unfortunately our limited resources (mostly volunteer - if you know of anybody who is interested in contributing please have them contact us) are focussed primarily on getting the next release 4.0 finished and out. That release is a major restructuring under the hood of how models are implemented that addresses the biggest issue from more advanced users that it be simple to add SasView models (C or python and which work just like built in models). It also is adding GPU support to help speed up calculations.
You can of course get SQ and P(Q) with the full model on the same plot (not sure about the distribution function) but it is ugly and a bit tedious. Basically you would check the theory curve and freeze it. Copy the parameters to clipboard then change the model to P(Q) only which should now show the P(Q) curve on top of the full curve and data. Freeze this theory curve again then choose the S(Q) model of interest and paste the parameters from the clipboard. You may have to hit "compute" after that not sure. As I said .. .ugly but right now best we can do. Of course you can save the curves as points in a file for future plotting in another package.
Unfortunately I don't think we can plot the polydispersity function at all right now which is clearly not ideal. I have added your request to the two tickets already open for these requests and suggest they maybe should rise higher in the priority list for our next code camp in October.
Hope this helps for now
Cheers
Paul