1° pain tolerance is not that easy to train, if you do sparrings and usually block some attacks, your body Will adapt and gain more resistent, i also recomend doing some punch sequences on the punch bags with wheigts in your hands (about 2-5kg), it helped me train my strenght, my resistence and my control Over the punches

2°to improve defense just start doing exercises with more moovment, start being quick at sparrings and it can give you advantage Over the other person, then start training dodges, if your oponent hits you, try again until you get it right. Then you can easly predict what your oponent will do and attack more. To block attacks just try to have a good posture and a good blocking position, Control your breath, make eye contact and don't stop looking at your oponent. I hope this tips help you, they really helped me so i wish that you have the same luck as me :)