To work in China long-term, you will need to get a Z Visa, and one of the requirements for this is a degree (which can be in anything). If you don't have a degree, your chances of finding legal work are pretty low. Unfortunately, that's the case not just for China but for most of Asia.
A DBS check (formerly CRB) is only available to UK employers. However, overseas employers might ask you to get a police check from Disclosure Scotland or similar to support your teaching application. I don't know whether a caution would show up on this, but if it did, it would undoubtedly render you ineligible to teach in certain countries.
Unfortunately, between the criminal record and the lack of recognised qualifications, there are very few options open to you. I'd recommend applying for a police check (https://www.disclosurescotland.co.uk/basicdisclosureonline/index.htm
) first and foremost to see whether the caution shows up, and then reassessing your options.