If spares are an issue, I would suggest throwing your spare ball during practice, at EVERY spare. Not just single pin spares, but buckets, or 2/8's(for the right handers), etc. In order to make the more difficult multi-pin spares, you will have to be extremely accurate. This will have some side benefits. Improving your spare shooting accuracy will help you hit your mark more consistently on your strike shots, which should help you strike more often. Judging by how often you say you miss the ten pin, it sounds as if you may not necessarily change your release when shooting at them. If you can break your wrist and come up the back of the ball, you can easily convert the 10 pin without a plastic ball. Just my $0.02. Hope the information helps.
