1. I think you are right tbh, I am building my own leads but I thought it might fast up the process and could give it a try.I will give you my opinion about question 1 : any and every data (leads) you buy, would be sold to multiple people and hence saturated and spammed by all the buyers like you and therefore a waste of money and a waste of time towards marketing efforts towards those leads that you buy.
Generate your own leads. That is the most effective.
And about question 2 : I've used MailChimp in the past and it was good.
Thankyou, I'm one step closerif you are looking only for E-Mail adresses check https://hunter.io/