No. Defense is very specific. For example, military cannot be used against the civilian population (though an interpretation of it being a broad category could facilitate this).
The typical anti-original interpretation. The only way the general welfare clause is broad is that it applies only under the enumerated powers. It was never intended as an excuse for government to usurp power and infringe on rights. But again, a properly narrow and originalist view would stand in the way of progressive authoritarian designs.