He has been in the USA over 4 years, working. He paid no taxes except some was taken off his cheque for 6 months. He has a ETA for Canada and he is worried when he goes to the airport if he will be deported back to Barbados. What should he do?
As I understand it.
The US will not stop him leaving, but if he leaves the US he will get a 10 year ban. If he lies about his overstay to try and evade said ban then that is grounds for a permanent ban.
As for Canada if they find out about his overstay they may well determine him to be at risk of overstaying in Canada at which point he is likely to end up being sent back to Barbados.
If you are a US citizen then you have the option of marrying him. He would then be able to apply for adjustment of status to lawful permanent resident. This is one of the few cases where someone who is not legally present can get adjustment of status.
Otherwise I don't really think he has any good options. It looks like he is probably stuck with a choice of remaining in the US as an illegal immigrant or returning to Barbados and not setting foot in the US again for at least a decade.