Broken Leaf Spring

I just got this used 5th wheel, it is a 2004 forest river cardinal 31 bunk model. It has been sitting at my folks place until I finished the hitch install, this was the first tow. It is a big awkward parking it at my house, but it seems while I was hitting a low spot, while the trailer was tilted someone to that side, it snapped front leaf spring... so down the rabbit hole I go.

Based on the sticker on the side of the camper, these are the capacities (much of it was faded, but the numbers were still there)

GVWR 5520kg, 12170lbs (the math works out)
Per axle weight rating: 2304 kg, 5080lbs

The dry weight of this RV is a touch over 9800 lbs... the 5080 lbs axle rating had me confused, but as I searched I found that the manufacturer figures in the weight supported by the hitch pin and the truck.

I'm thinking that if I replace one spring, I should replace at least both sides of that axle, and if replace them on one axle, shouldn't I replace them all? These springs are 20 years old as far as I know.

...and if I'm replacing them all, shouldn't I perhaps go to a heavier spring in hopes to avoid breaking another one, perhaps 6k springs (3k per spring)? Based on how this sits on my truck, another inch or two in height on the RV would be helpful as well to level it out.

Thoughts?

Thanks,
Scott