Upvote:2
From Helsingborg you're actually pretty well situated.
If your scheduled train happens to be canceled, you can hop on one of the frequent ferries to Helsingør and take a train on the Danish side instead. These trains are part of the Øresundståg system too, but the service on the Danish side is a lot more frequent, so even two cancellations in sequence would delay you only 40 minutes.
Furthermore, in case of trouble developing close to the airport, you will be in a better position if the train dumps you out in central Copenhagen (with metro and bus connections going to the airport too) than if the Swedish-side train is terminated short in Malmö.
Also, you already have an extreme amount of buffer time in your plan. The 09.11 train you're planning to catch is scheduled to arrive at the airport four and a half hours before your flight departs. For a Schengen-internal flight in the middle of the day, I would not worry about getting to the airport more than an hour in advance.
Really, with that much landside buffer in your schedule, the more relevant risk would be that the flight itself ends up cancelled, say, for mechanical reasons.