I have used a rachet strap to press a bow just dont press it way down passed what the bows limbs go at full draw i hooked the special hooks in the limb pockets and went down real slowly the string start to sag then i stop did what I nedd to do and then with some help carefully draw the bow with your foot and have a buddy take the strap off with the buddy taking the strap off when the bow is draw you avoid the fast pop out that rachet strap are know for it worked for me in a pinch but do not advise to use for daily use
I am not liable for anything in case of injury like i said did this in a pinch!!!
Firstly you didn't hook anything into the limb pockets, they are at the bottom of the limb at the riser.
Secondly, you can back a ratchet strap off slowly, you just don't know how. You can do it, and I have done it on my bow before.
If you are dead set on making your own "portable press" here is what I did.
I took two pieces of square stock bar steel, .5"x.5", cut one piece to approx 3" and the other piece to approx the width of your limbs (2" or so). Weld it together at a T. You need to bevel the 3" piece at the end so you don't have a huge glob of weld. I used a tig welder and beveled the edge before I welded it and there was no hump. Then, you want to drill approx a 1/8" hole through the center of the long part of the T. This is the part you will insert down through the end of your limb between the limb and cam/idler wheel. Use structural wire you can buy at home depot, it's really cheap. I can't think of the proper term for what it is, but it has very high load ratings. run it through the hole, and connect it so it's a solid loop that won't come undone (they make special parts for this too, once again I don't use these on a daily basis, so I can't give you a specific name).
Build two of these.
stick one through one limb, one through the other. insert ratchet hooks (buy a good ratchet) through the wire loop, and tighten until your hearts content.
if you're not a welder, i wouldn't suggest you doing this, because if you don't get good penetration it WILL fly apart at the welds.
Learn how to use your ratchet strap and you can back it off one click at a time.
I built one of these a while back, and used it sparingly. I mean, VERY SPARINGLY!
I'd just buy the bowmender bow press or any other portable press you can, they can be had for as little as 30-40$ I believe.
good luck!