A few things you might want to consider.
Are you going to be paid by the HOA or is this "managed by a agency that corresponds to the HOA" a property management company? If it is a property management company, I would personally be out. The current provider might not be doing what they are supposed to, but then again they may be owed so much money that they are giving the HOA bare minimum with a one finger salute.
When looking at your price breakdown I did not see a place that you accounted for leaf clean-ups and I know you said you are going to be mulching trees. If these are deciduous trees you need to remember the leafs.