Question

relationship between the enthalphy of reaction and bond enthalphy

Answer 1

You are confused as to why we take "reactants minus products" when calculating the enthalpy of reaction based on bond enthalpies.

Consider as reference state all your reactants and products in their atomic states, that is, with all bonds broken. Forming a bond releases energy, so the reactants and products all have a negative enthalpy

ΔH=−∑ΔHbonds

with respect to this reference state. The enthalpy of reaction remains

ΔHrxn=ΔHprod−ΔHreac=−∑ΔHbonds,prod−(−∑ΔHbonds,reac)=∑ΔHbonds,reac−∑ΔHbonds,prod,

so the inconsistency you've pointed out is just the neglect of a minus sign.