Say a peasant had a crippled child or infants to care for or nature was not cooperating or all of the above. Was it possible to appeal to his local Lord for a reprieve on his obligations? Obviously it would depend on the Lord’s character but I’m curious if there was flexibility in the system given 100% exploitation all the time seems like an impractical model yet on the face of it feudal contracts seem hilariously one sided and unfeeling.

Yep, happened all the time. Feudal obligations were very much tied to all kinds of traditions, which included things like tax or rent exemptions for a given period or privileges (collecting firewood from the lord’s forest, being allowed to trap rabbits in the lord’s deer park, gleaning grain after the harvest on the lord’s fields, etc.) or even donations (old clothes, leftovers, maybe some money). 

So there was always a back-and-forth, where peasants pushed as far as they think they could get, and lords always had to shift on a spectrum from granting those favors when it suited their interests to be seen as generous to denying them if they felt their revenues were being cut into too much. 

It’s actually not that different from the ways that scholars of slavery have talked about slave systems involving both resistance and accomodation as well as terror, brutality, and exploitation.