5'1 Inverted LW - need advice on cutbacks and energy pacing

Hi, I'm 5'1, 31 kilograms and U15 (right footed). I played my first 90-minute game on the right wing, played well defensively and made our only big chance, but gassed completely and fainted at 88', hurting my knee in the process. I'm currently recovering and trying to do upper-core exercise while my knee heals. I'm also switching from RW to inverted LW and I have a couple of questions:

1. Best seated or bed core exercises for shooting torque while my knee heals?
2. Once healed, what solo drills help keep the ball tight (within 1 ft) during a high-speed cutback?
3. How do lightweight wingers pace themselves so they don't crash before 90 mins?

I understand I'm very underweight and currently working on that to bulk up to a healthy weight range.

Also, if any experienced coaches or wingers are down to offer occasional feedback or check my progress down the road, I'd really appreciate it. Thanks!