How would you restore sweetness and moisture in this bundt cake?
My suggestion would be to just go with the sugar increase, it might be sufficient to increase moisture. You can combine it with less baking time, if you want to - try using a thermometer and bake to 94 C, maybe 96 if it gets out underbaked. 

If it still feels dry, you should add fat, not water. Increase the butter, and maybe add one more yolk. 

You can also use an artificial sweetener instead of sugar, but it will again increase your dryness problem. An interesting option would be to use another form of sugar - replace part of the original sugar with some molasses or a syrup (corn syrup, agave syrup, whatever you find). It will make a moister, heavier cake, but also change the flavor profile. 

I must also say that people rarely find pound cake to not be moist enough. If you don't like it that way, you might be the kind of person who likes cakes extra moist, so it might be worth looking into cakes soaked in syrup after baking. You will find most recipes for that from Middle Eastern sources. If that's what you like, you might want to try syruping this one too, it will solve both your moisture and your sweetness problems.