55lb is a bit high just to jump in unless you are a pretty strong guy. The muscles for drawing a bow aren't commonly used apart from drawing in the bow.
But you should be there pretty quickly. Also, technique makes a big different. Video of you drawing would be the best way you could get a critique online, but just watch some good demonstrations, or see your local club, they'll help you. The best description I can write for you is the Keep your Elbow high, and spread your shoulders. Don't use your bicep.
If you are left handed, that makes more sense with what I was seeing. It'll probably be a little technical for you, but I follow the advice of my friend Zan Christensen when tuning a bow, and it might help you understand the dynamics of your arrow flight a little more.
http://www.bowhunting.net/artman/publish/Zan_Christensen/Tuning_Your_Bow.shtmlI honestly wouldn't bother building any arrows for your 25lb bow, if you have a group that shoots from them okay, I'd keep them and save your money for a decent set for your 'real' bow. There's a guide in my sig which is a good starting place on building arrows, and lots of advice online.
What modifications did you make to your bowstrings?
Do you know your draw length? I commented on your youtube video with a suggestion on improving your target, which you'll definitely want to do with a 55lb Bow.