Add punctuation: It has not been possible to perform a validation of the model against experimental data since a sufficiently controlled set of data was not found
A: It has not been possible to perform a validation of the model against experimental data since a sufficiently controlled set of data was not found.

Add punctuation: 214 or to rulers as sent by him for vengeance on evildoers and praise to them that do well
A: 2:14 or to rulers as sent by him, for vengeance on evildoers, and praise to them that do well.

Add punctuation: It would be horrible because I would feel guilty that I could not do anything to prevent her from being shot and would I be afraid of seeing everything around
A:
It would be horrible because I would feel guilty that I could not do anything to prevent her from being shot and would I be afraid of seeing everything around.