Is 1 mg a day from 0.5 mg a day of clonazepam a big increase in dosage for panic disorder or not really?

Not really: but benzodiazepines should rarely, if ever, be the primary treatment of panic disorder. I see you are on a beta blocker, and those can help somewhat as well, but the primary treatment is generally with a combination of psychotherapy (cognitive behavioral therapy) and SSRI/SNRI antidepressants. Antidepressants can prevent panic attacks, while benzodiazepines really do not. Benzos should be limited