My experience.....

...with nothing modified on the biscuit I would say approximately 6-8 fps. With the biscuit modified slightly by trimming some bristles, etc.. I would say 3-4 fps tops.

As for compared to a "drop away" rest, night and day in my opinion. The Drop away rest is designed to provide minimal contact with the arrow. Less contact equals less friction. Less friction means less of a reduction in arrow speed because of the contact.

As for how it fairs as a hunting rest....take that with a grain of salt. If you are shooting a decent setup then even 6-8 fps is not that big of a deal provided your bow is well tuned. It has other attributes that more than make up for the marginal speed loss.

A rubber tubing peep sight definitely decreases arrow speed. Again, my experience is that it could be as much as 8-10 fps...depending largely on the position it has on the string. A Fletcher Tru-Peep or one of a similar design is likely to only reduce speed by approximately 3-4 fps.

As for your particular setup...you are "losing" about 18 fps because of the shorter draw length and heavier arrow which would bring your speed down to about 290 fps. Give or take 5-8 fps for how some manufacturers are "off" on their speed ratings and that brings you down to about 282 fps. A rubber tubing style peep sight would knock another 8-10 fps which would bring you down to 272 fps and a whisker biscuit would bring it down to around 264 fps. Throw in some string silencers, a rubber eliminator button, brass nockset and/or a loop and we are down to about 250 fps.

240 fps seems a bit slow but not by much considering what could be in the rest of your setup.