The wing hold down is the wood supports where you insert the wing bolts to secure the wing to the fuselage.

I respect your openness regarding your skills. Many pilots won't admit this, or they just don't have the brains to know the difference. Losing a few airplanes is an amazing teacher. You are doing fine by realizing what you can and can't do already. Believe me, I know the feeling. As you develop your skills, you will eventually want the airplane to do more, or you may become bored with it. So, you can set the airplane up as the books indicates for the fun stuff that will come as you develop and want to try new things.

You should always be aware of adding weight to any airplane. This specific airplane should be just fine for you as long as you don't get it too heavy and too over powered. I flew a friends with a 61FX in it. It was not as agile as mine with the 46 FX. Just my observation and opinion. You have to make your own decision and other pilots certainly do put larger engines in theirs.

It's really a fun airplane. Think you will really like it.