TBH that rim joint is pretty corrroded. I bet the rim is full of water - do you ride in all weathers and on salty roads? If that's the case it's likely that the nipples are corroded to the spokes and the tension can't be increased. If pressing down on both sides of the rim with the axle on the ground produces creaks I'd say the spokes do need tightening or there's a cracked flange. Get it inspected by a mechanic at a decent shop, not at a bike supermarket.
Have you also inspected the frame carefully for cracks?