Can histamine potentially disrupt normal cell cycle, and in high enough concentration disrupt apoptosis? is that why stress causes so many problems?

Not known: I am not aware of any effect of histamine on the cell cycle. Histamine is also not usually associated with stress although there are many other cytokines which are.

Not clear.: Histamine can effect apoptosis of certain types of cells like monocytes or keratinocytes. This does not necessarily indicate that the same effect occurs with other cell types. Histamine is also a neurotransmitter effects the brainstem to cause wakefulness. This is why centrally acting antihistamines cause drowsiness by blocking this effect. These effects may be unrelated to stress.