What are the red lines in terms of relationships between Officers and Officer Candidates?

Pretty sure that falls under fraternization and it's a no-go.

I suggest reading through the Federal OCS handbook for clarification: http://www.benning.army.mil/infantry/199th/ocs/content/pdf/OCSOP.pdf

Generally speaking, romantic relationships formed during Officer Candidate School is frowned upon. Candidate-Candidate relationships and Candidate-Cadre relationships are explicitly forbidden. Anything else that falls outside of fraternization would still be ill-advised. OCS is only a limited amount of time; love can wait.

"What should be done if the officer puts in awards for the OC for things he/she did not do? "
A quite and simple conversation..

Sir, you can fix this, or I can.......Do the right thing because its the right thing to do, or I will follow that same idea and this will get fixed in spite of you, not because of.