This question titled 'DDoS and Shared Hosting' was closed as "too broad".
What should I change (e.g. what should I add, and/or what should I remove) in order to make this a question which you consider reasonable?
Limit yourself to one question. You have a bullet list of multiple questions. The question is too broad because it is asking too many things.
Your sub-question "Is there any commercially-available service..." is off-topic here. Questions that ask for third party resources, software, or services attract too much spam and self promotion. Take that one out for sure.