Yes these sentences are perfect. And using the Past Perfect Tense is the correct form! :) Good job!

The short answer is yes, you can use both present perfect and simple past tense after 'since'. But there seem to be many conflicting arguments about this among native speakers, so it may not be all that clear cut. This BBC page might be a good guide on this subject (look for the "pasta" example): http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv174.shtml

As Ezekiel, a native speaker writes, using the Past Perfect Tense is the correct form. Using the simple past tense after 'since'is generally done by people whose first language is not English, and who are relatively uneducated.