Regarding using stops in abbreviations, it's been the practice for quite some time now to omit them (New Hart's Rules / The Oxford Guide to Style). I'm also happy with that one - makes writing less cluttered. The TNA is extremely inconsistent with RAF, R.A.F. and R A F, for example - beware when using their search engine.
The 'rules' are complex, but generally a stop is used on a truncated word, e.g. Prof. for Professor, but not in a contraction - if the final letter is correct, e.g. Dr for Doctor. However Street becomes St. to differentiate it from St for Saint.
To be honest it gets very very tedious obeying these rules as exceptions keep appearing. I'm going to the pub .