I'm starting to get worried that your a worrier (probably because I'm a worrier). I think you should add in, in addition to posting on BL, doing your own research on shit via google, or whatever. You'lll get more info and you will get it quicker. Since your a worry wart (not an insult, I'm one myself, and I could be wrong and your not one, if so- apologies bro) by googling stuff like benadryl and doses and stuff you'll get more info quicker and might also get other info that will be helpful that's related. I think you should add in more resources to figuring out the stuff your trying to sort out than just posting on BL. I'm sure most ppl do and I'm picking up anxious vibes from you, it feels like your sitting on the edge of your chair waiting for the next response from someone here after you make a post.
If accurate and helpful info is what you seek, and if it will also help you chill a bit, you should be doing that if your not already (and maybe more of it).
That much benadryl doesn't SOUND dangerous to me, but if I was in your shoes with that question I'd be searching on the internet for answers and not just posting on BL waiting for someone to give you an answer.