Contractor Among Contractors
I would not be so certain that OP is necessarily an employee.
Are the people in Brazil and Canada employees or self-employed/independent? If they are not employees, it would be easier to argue that the change in locale is indicative of a change in status. Employees on site, contractors off-site and out of the country.
How much are you supervised in your work? How much supervision / direction / control is there? You said "documentation organisation" -- are you making organisation decisions, or are they making those, and you implementing them?
Is it feasible for you to do this work on a fixed cost rather than hourly basis? If so, that would probably yank you right out of any IR35 / employment concerns, if you've been hourly before but are fixed cost now.
How much Mutuality of Obligation is there going to be?
Do you have employee benefits now, and will you be forgoing any of them? Or, would you be willing to forgo them for a higher rate?
Before just saying that I was inside IR35, I'd read up on it and consider a restructuring of your relationship, if possible, to put you outside it. If you can get an IR35 friendly contract, it is going to be difficult for HMRC to prove you are inside, because they can't compel the engager to discuss your case with them. You can give them the contract and have someone (IPSE or QDOS) represent you, and they will probably go chase someone else. And honestly, at 60% time and at your age, you aren't likely to be worth chasing for them anyway.
So that's where I'd start. See if you can structure things with enough changes to justify an outside-IR35 status, and then probably go sole trader.