Your available bandwidth is based on your usage over the past 7 days. It is a factor of: 1. your usage over the past week 2. the amount of SP you have 3. how busy the network is at the current point in time.

You can see your current bandwidth at steemd.com/@stimialiti

You would have to dig into the code to see exactly how much each operation costs. I do not have the answer to that.

Viewing does not cost anything. It only charges for transactions that you submit to the blockchain. Pictures are not stored in the blockchain - only the URLs are, so they should not have a very big effect.