Awww sorry you are having a rough go of it. 🙁
So at the moment he is probably getting more afraid because he knows the medicine is coming, but that should be temporary. For now, you will just need to resolve to take a tough-love approach, because he does need his meds. I find it helps to take some deep breaths so I stay as calm as possible as well. Some buns do better with giving them on the ground, but I usually either sit the bun on my lap on a towel while I sit on a chair, or put the bun on a towel on the table. What meds is he on? These videos have some helpful tips on syringe feeding medication (liquid meds too):
https://www.youtube.com/watch?v=qmlx_K9RS0A
https://www.youtube.com/watch?v=xaHtUy4EX5s
Regarding the chewing etc, some buns just aren’t great candidates for unsupervised free-roam. But as long as he has an x-pen that is fully bunny-proofed, you can lock him in there when you can’t supervise, and then you can let him out for play time each day. Since he was in such a weird situation before, you might find he feels safer having his own smaller space all to him-self as his “burrow”.
For chewing, heavy ceramic tiles are useful to block problem areas, and most buns seem to love shredding phone books (if you can find one!). My big chewers also like cardboard cat scratchers and grass mats. The combo of blocking problem areas and giving safe alternatives should help!
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.