Glad you made it to the forum.
Your boat, indeed a Monaco II
is equipped as a beach sailer, as some Minisails were sold and used back in the 7'ties (love the four added handles at the corners by the way)... And that's fine because they were designed for this purpose.
Their potential to get competitive in clubracing with them, led to various improvements making the boat much more performant.
Yours as it is now is original, let's think you want to get out sailing and have some fun asap. Well, without a new sail and a stiffer boom (the lower horizontal spar) you don't need to bother about pulleys for a boom vang.
The combination of a "bendy boom" (the 35mm one you have) with a strong vang will make the boom bend more making you sail even fuller, just the opposite of what you wanted.
So if you sail with the original boom, the simple fixed rope will do fine, just to keep it from skying up during broad reaching and running.
Yes, you can make the Minisail better in going upwind (or going upwind at all), that would require a stiffer boom and a good sail. For the boom vang then there are some proven ways to get around that.
Will need to digg in the archive to give you some pictures explaining this.
Untill then, have fun with the boat.