There's probably better Benzos than lorazepam for an acid comedown, but if that's all you have access to it'll still help. Benzo overdoses are really rare by themselves, your need like at least 10 mg to be anywhere near possible fatality, probably more like 20 tho, but you'll feel like shit the next day if you take too much. Mixing Benzos with some other drugs is dangerous, but not with acid, so your fine. 5 mg is a lot, but it isn't dangerous