i certainly agree that tyrod was a reason watkins never had huge numbers here, but in my opinion, you are down playing his injury history way too much. even with the rams he not going to put up huge numbers due to qb play. i liked your estimate of 1150 yrs and 10 tds as his ceiling, but i think we both agree he can do better with an established qb...as long as he healthy.
the rams could be in a tough spot. they need to come up with a reasonable contract soon the sign sammy, and if smart, he'd take it. if he has numbers like you mentioned, i'd guess he'd want to test the market, and possibly find a better situation for him. likely the rams will over pay now and take a chance on his health, which i question. it's not a terrible gamble, so for the rams i think it's worth it.