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Yes, you can do this. This article has more information about that:
https://www.gardeningknowhow.com/edible/vegetables/vgen/preseeding-vegetables.htm

Yes, sulphate of ammonia will speed the composting of pea straw. Fresh lawn clippings will do the same thing. The following link is to a forum discussing sulphate of ammonia in composting: http://forums2.gardenweb.com/forums/load/soil/msg031010382356.html

This is a difficult question to answer. Any suggestion would be based on many factors: your preference of pea (shelled, edible pod, snow), soil type, zone, ect. Ask gardening friends which pea they think performs best in your area.

"Deadhead spent flowers and remove seedpods to promote re-bloom. Caution – sweet pea pods are not edible, they are poisonous if ingested. " Taken from this link: http://ext100.wsu.edu/clark/wp-content/uploads/sites/7/2014/02/SweetPeas.pdf

You probably have too much nitrogen in the soil. You can 'sweeten' it up with lime. Too much nitrogen grows beautiful, lush, green plants with minimum yield.

The following link will take you to a page of articles on the subject: http://www.google.com/cse?cx=012078378210706707791%3Af1h5n_k1r5e&ie=UTF-8&q=too+much+nitrogen&oq=&gs_l=#gsc.tab=0&gsc.q=too%20much%20nitrogen&gsc.page=1

California blackeye--Bush, Pinkeye purple hull--Bush type, Cream pea 40--Both Pole and Bush available, Zipper cream pea--Bush, but Pole may also be available, Contendra pea--(not familiar with) Do you mean Contender? These are available as Pole beans, though bush may also be available