Finding the union, subtraction, and intersection of two DFAs
Yes, your understanding on point 2 is correct.

Your understanding on point 3 is mostly correct, except where you say "mark final state as explained in 1st bullet point in point 1".  That statement doesn't type-check, as you can't do that to the $\epsilon$-NFA.  If you've created an $\epsilon$-NFA, then its states are of the form $S_1$ or $S_2$ (where $S_1$ is a state of DFA1 and $S_2$ a state of DFA2), not of the form $S_1S_2$.  So, it's not an option to mark $A_1F_2$ as final, as that's not a state of the $\epsilon$-NFA.  Fortunately, you don't need to do that.  You create the $\epsilon$-NFA as you described, then that works immediately with no further changes needed.  The final states of the $\epsilon$-NFA are the final states of DFA1 and the final states of DFA2.  (Perhaps you are thinking: create the $\epsilon$-NFA, convert it to a DFA using the subset construction, then mark final states specially.  But there's no need to mark final states specially: the subset construction already takes care of marking the final states correctly.)

No, you can't do this for intersection or subtraction.  Try it on some examples.  I think you'll quickly be able to find some examples where it goes wrong.  Also, my comments about point 3 apply here as well.