I have been using closed (soldered) sterling silver jumprings in combination with lobster claw clasps instead of the small rings that are often included with the lobster claws. I am unable to pull the rings apart with force but still worry that this is not the most effective and safe closure. Any comments as to whether this is a good combination, or any other suggestions?
Using a soldered closed jumpring is a very safe and effective component for this purpose. Split rings are a very secure alternative to jumprings yet still allows attaching other jumprings or split rings. The use of jumprings or split rings also allows you the option to attach a larger ring for ease of use.
Another option is to use an extender chain, this gives you strength and length adjustability.