You can broadcast the borax, but that is just more trouble and through the skimmer is just fine. No reason not to make it easy on yourself. Plus, sometimes the Borax is clumpy and if you add it through the skimmer, you can see the clumps and break them up.

A pH of 7.4 is just perfect. Don't fight it. Topping off with your tap water may increase the pH some, but with only an inch or so being added, it isn't going to affect it too much.

Glad your water looks great! It's amazing what a little knowledge can do for your pool, isn't it?