UK national, 'L' visa, 180 days per year?

Validity: 2 years from September 2018
Entries: Multiple
Duration of each stay: 90 days

Hi, I'm wondering how many days I can spend in China within one year as a UK national with this Tourist L. I've seen some accounts saying there is a 180 day limit on stays within a single one year period. Is this the case? I can't find reliable sources to ensure it, but it would make sense, to prevent people from basically living in China.

I first entered in October 2018, left after 90 days in December 2018 before re-entering that same month. I will currently have to leave China on March 15th. Will I then be unable to reenter on my current visa until a full year has passed (October 2019) since my first entry, as I will have stayed in China 180 days already?

I am working towards getting a work permit with a legitimate and reputable employer who has offered me a job. For various reasons I won't go into, the job will not begin until after March 15. I just don't want to have to go back to the UK while I wait for the work permit to be processed, I'd rather stay in China if I can.

If anyone could clear this up for me that would be great! Also, is there an entity within China that I can ask about this without risking their suspicion?

Thanks for any help!