I don’t use the bunny burrito on mine, it isn’t secure enough for me, Powder is pretty large (8lbs). What I did for holding was boyfriend held them against his chest, one hand on the shoulder blades (this prevents a lot of struggling in my buns) and another supporting their back near the tail, with his arm pressing lightly across the rest of them. Mine won’t fight or struggle when held like that (only way they don’t fight us), but the vet also holds them on a table with slight pressure on the shoulder blades, which could work since yours bites. For giving the meds, maybe wear some gloves in case of being bitten, but there is a way you can hold the head so they can’t move and your hands are safe from bites. I had to secure Stickers head so she would stop thrashing it around and spilling her meds everywhere, then the brat tried to push it out of her mouth with her tongue lol
Our vet showed us several ways to secure her when I had to give her meds, maybe yours could give you tips on how to make it easier? Mine didn’t take to the pineapple flavoring, she knew it was medicine! Even though the vet was surprised cause “most buns eat it like candy”.