1. yes
2. yes
3. it will affect your isp who will not appreciate that and probably come down on you.
If you need to send newsletters to a large amount of subscribers, leave the actual delivery to the professionals. I know you're looking for a cheap method, but you get what you pay for. You CAN do it on your own, but since you don't have a lot of expertise about email and your ISP probably has policies against such behavior, your actual delivery success rate will most likely be pretty low. Email can be a tricky business making sure it gets delivered and not detected as spam.