He has filed a claim with the government claims board and it was denied? This must be done prior to filing a lawsuit if you intend to sue the county. I believe the statute of limitations is 6 months and a day. Contact a personal injury attorney ASAP.
The jury might hear your statements with the caveat you were on medication for ADHD. Your ADHD and medication is relevant to the weight and/or interpretation of the statements, not their admissibility.
A dismissal pursuant to PC1210, aka Prop 36, would not prevent someone from owning a firearm assuming they are otherwise lawfully entitled to own said firearm.
Even without any criminal history, it may be illegal to own tear gas/taser guns etc. I would consult an attorney prior to purchase.