How did Evans appear which prompted Jackson call him "scruffy sod" ?

And 1 more thing - who was the senoir amongst these 2 officers ? - Stephen or Jackson ?

We could not find any instance where Jackson actually called him a "scruffy sod". It would be helpful if you mention the page number where this can be found in the chapter. 

The answer to the second part of your question is as follows:

Jackson was the "senior prison officer" while Stephens was "only recently recruited to this profession". Therefore, Jackson was the senior amongst the duo.

(Due to paucity of time, it would not be possible for us to answer all your queries. However, three of your questions have been answered by us. Please try to answer the rest on your own and revert to us for feedback. We will be happy to help you suitably.)