Hosting question

Any shared hosting will suffice (especially if they offer lightspeed server). I have about the same amount of traffic as you do, and I host with @DamoHG; their lightspeed servers and shared hosting handle all traffic, and my sites load extremely quickly. So, yes, shared hosting with a good host will suffice.

Well with your visitors any host will do good ,but i dont think its a problem on how many visitors you have on site its about your content you need to upload and you need more space .I think traditional host like bluehost etc its very good you take a normal package and in the future you need more space you just upgrade for a biger package

Any is fine. 400 is not much. you can even do shared server