Hey! I'm so glad you played and enjoyed it!
Paradox is cumulative. The character is not required to rest to reduce it, it is just something that can be done. Each backlash and each entire day without performing magic recovers 1 point towards the Paradox threshold. If you want to take a risk, the character can have several consecutive backlashes before deciding to take a day off to recover.
Any magic that a sleeping observer would not notice or view as a mundane event is coincidental. Magical perceptions are good examples of coincidental magic.
If the character talks to inconspicuous spirits, a sleeper might only see it as a lunatic talking to himself. However, if the character causes a spirit to act physically, such as commanding a wind spirit to lift him or a storm spirit to suddenly change the weather, then we could consider it vulgar magic even if the spirit itself is not seen.
It is worth remembering that several "coincidences" happening successively in a short period of time begin to seem too unlikely. Ultimately, the GM is the arbiter over each event.
Thanks for the question and good gaming to you!