Brake assy's typically are setup for RANGES of weight based on the DRUM SIZE.
IF you have a 10" drum on your axles then the brake assy for 3,500 lbs SHOULD BE correct.
The next size up is 12" drum which typically is used on 5,200 lb and higher axles.
7" drum and brakes are typically used on axles below 3K lbs.
You could CALL Etrailer and ask for technical help, most likely they will confirm 3,500 brake assy for 4,400 axles.
I have axles rated 3,300 lbs per the tag and have 10" drums, 3,500 lb brake assys fit and work perfectly.
And, 2016 trailer that is only 3-4 camping seasons, what the heck did you do to NEED to replace the brake assy's? I replaced ORIGINAL brake assys on mine two yrs ago and it is a 1980s 26ft TT..