In my experience, chewed sinew gets swallowed.
Just set it in a bowl of slightly warm water, or if you have the self-control, lay it in your mouth for a bit...I mean little while. Chewing will tear up the fiber some and weaken it. I don't pound it, either. I use back sinew which is very fine. Just bend it around until the strands separate, and tease them loose with your fingers. For my first set of arrows, I used pine pitch to set them, and waterproofed the hide-glued lashings with a mix of pine pitch and deer grease. The mix has to be just right to avoid cracking in the cold or rubbing off in the field. What a pain. Next set I will use sinew, again, and superglue or poly to waterproof.
I am shooting these out of glass backed recurves and longbows, they don't have to be true to the memory of Ishi, for crying out loud. About the poundage, I don't see a problem. I was drawing about 44 pounds when I killed Ashly at 25 yards. Point put a hole in a vertebra on the back of her neck as she turned to flee. If I had known that it was 25 yards I likely would not have shot, but I didn't, and it felt right so I did. Arrow went right where I wanted it to, but the dang deer was a real quick turner! If it could pierce a vertebra, I have no doubt that it would have found her heart if she had just stood still.
After the shot:
Killdeer