There are three main things to tuning a recurve. First, start off with correctly spined arrows. After that, it's brace height and nock point. Adjust the nock point to eliminate porpoising. Raise brace height to eliminate fishtailing. You want brace height to be as low as you can get it while also getting a quiet shot and good arrow flight. I like Fred Asbell's method: Lower your brace height untill you start getting noise and bad arrow flight, then start raising it up until the noise goes away and your arrows fly straight.
You can also experiment with building out or thinning down the strike plate, but that's usually not necessary.
Your bow was made by Bear for sale in a department store at a bargain price. I don't remember whether it was made for Sears or J.C. Penney or Montgomery Wards but it was one of those three. Since it was meant to be a budget bow, they didn't spend much time checking actual draw weights on the finished bows. That's why it's got that 50/55 mark. That is the draw weight range they were aiming for. It might be pulling 50 at 28 or it might be pulling 55 at 28, or anything in between. Plus you're drawing an extra inch further than marked, so there's another 2 1/2 - 3 pounds over and above the marked draw weight that you're pulling.
The only way for you to know what you're drawing is to draw an arrow to anchor and have someone mark the arrow even with the back of the riser. Then get on a bow scale with the arrow nocked and pull down until the back of the riser is even with the mark. Have your helper read the poundage on the scale.
Arrows are spined assuming they will be 28" long with 125 gn tips. Shorter than that and they'll spine stiffer. Longer than that and they'll spine weaker. For every inch of length shorter than 28", subtract 5 pounds. For every inch longer than 28", add 5 pounds. For instance, if your bow is drawing 50 pounds at your draw length and you want arrows are 30" long, you add 5 pounds per inch. You buy arrows that are marked for 60 pounds. If you want 26" arrows for your 50 pound bow, you buy arrows marked 40 pounds.
Then you subtract 5 pounds for every 25 grains of tip weight under 125 gns. Add 5 pounds for every 25 grains over 125 gns.
Your shooting form - most especially your release - has a lot to do with how your arrows fly, for sure. The best way to get a clean release is to not turn loose of the string. I know that sounds wierd but hang with me here.

There is a fine distinction to be made. The key to a good release is relaxation.
If you turn loose of the string, that's a physical movement. You will risk moving your hand away from your anchor point which will throw the shot wide left or right. You will never be able to open your fingers fast enough to get them out of the string's way, so forget about even trying.
The string is trying to get away from you from the time you begin your draw and you're hanging onto it to keep it from getting away, right? So.... Instead of opening your fingers and turning loose of the string, you simply relax your fingers and let the string will push your fingers out of the way. When you're ready for the arrow to go, you just stop holding it and allow the string to escape.