Adding some extra muscle meat is not a problem, they usually have a problem with too much organ meat rather than too much muscle meat. The guideline for bone is roughly 5-10% of their diet. There is calcium in muscle meat as well so it's unlikely to create a difficiency of calcium by adding some extra meat. I did actually have Duffy on only chicken muscle meat for a couple of weeks by her homeopath vets recommendation after a IBD episode, but not something you would do at any other time.
Normally it is not an issue with small bone slivers as it will be digested, but absolutely you can take them out if it concerns you, I used to remove the larger pieces from Duffy's food before I needed to switch her to boneless (using
TC Instincts Premix) because of the IBD issues.
Some of the commercial raw foods do have small bone chunks that pass though the bone sifter, unless they triple grind the bones which I know not all do. Unfortunately all the companies I'm familiar with are not available in Winnipeg as of yet, they are local BC made some suppling outlets in AB, Ont & Qc though.