Or, like many other people have done here, find a camping cooler that’s the right size and cut a hole into the lid.
Or, most likely as a zero-cost option, pop down to your local greengrocer and ask whether they have any spare styrofoam broccoli boxes. They are waterproof, light, and insulate extremely well, and it’s easy to make a hole in the lid with a piece of heated fencing wire or similar.
The jury is out to be honest. I bought a gastronorm 1/1 150mm deep stainless steel container for €10 last week. Cooked 3 racks of baby back ribs with plenty of room and no bad smells. This is what I’ll be using from now on.
Seeing that you have your food hermetically sealed in bags anyway, health issues are not something I’d worry about. The Ikea box is made out of PP (polypropylene). That’s not terribly suitable for higher temperatures. Once you go over 60-65 ℃, the plastic goes a little soft. It’ll smell of plastic a little. Once you go towards the boiling point, the container may deform (although I wouldn’t expect it to melt outright).
I’d be inclined to give the Ikea box a miss and go with something more suitable, such as a polycarbonate container.
I’m sorry, but I can’t tell you. No first-hand experience. If you want to give it a go, I’m sure you are not going to poison yourself or anything like it. With the food in a vacuum bag, you could probably cook it in a bucket of motor oil and it would still be fine. (No, i’m not suggesting to do that )
If the plastic smell annoys you, stop using that container. If the container deforms at higher temperatures, stop using that container. If it all works and you are happy with what you are getting, keep using the container.