Re: First time on the water today, I could use some advice!
Avenger's comments about having an engine and his Wife's comfort level are excellent advice. Yes, you'll use the engine less and less as you acquire sailing skill, but get one anyway, even if for no other reason than marital happiness.
Our previous boat was a fractionally rigged h260, which I tried sailing with jib alone, with results similar to yours. While masthead rigs can sail quite well with headsail only, our
h260 would not sail to windward and was almost impossible to tack.
You asked about determining proper CE. Since your boat is tiller-equipped, I suggest you'll soon develop the "feel" for when your boat is/is not properly balanced, in addition to extreme healing and rounding-up.
I don't recall seeing anything mentioned yet about reefing the main. Presuming you have some method of reefing your main, I suggest you practice that procedure to make absolutely sure you know exactly how to get it done quickly, before you actually need it.
Then, keep in mind the truism that if you only think you might need to reef, DO IT.