Neem or any other oil is of no value with slugs or snails or for that matter with mice: the value is with insects.
And your dilution rate is not very weak - its the standard one. Actually 0.05% by volume is right ; and 32 (fluid ) oz = about 1 litre or 1000 ml ; and 1 standard teaspoon = 5ml. so 5:1000 = 0.05%.
I keep a bottle of this mixture ( an ex-kitchen cleaner trigger operated spray bottle, well cleaned out ) using a proper horticultural wetting agent ( surfactant) added in the same proportion, and whenever I see anything doubtful, a quick swoosh sprayed on is helpful. I don't use washing up liquid as the surfactant since they often have glycerine added ( to be "kind" to your hands) and that tends to block up the pores of the leaves when it dries. Your actual horticultural wetting agent avolids that.