I trailer not only my own boats, but lot's of boats through the business - a good amount are heavier than what you're looking at, as well. Personally, I wouldn't invest in any fancy weight scale things built into a hitch. I just don't trust that it's as strong as a hitch bar without that built in. I could be wrong - but that's my thought.
A better way to go would be a tongue weight scale. However, with a little mechanical leverage, you can use a regular bathroom scale to weigh things that are well above the bathroom scale's ability.
Regarding WD hitches... I've never used them - in addition to what was mentioned by Family, I had found it hard to get it to work properly given the surge brake actuator.
To quickly revisit... highly consider EOH. Once you go EOH, you won't want to go back to slow/unresponsive surge brakes! Although, switching to EOH may bring WD back into the picture, if you want.
If the trailer doesn't have brakes on all axles, does it have the backing plates to add brakes? In some states it's required by law to have brakes at all wheels.
Side note... I take trailering safety very seriously. I HIGHLY suggest you take time to get used to it - find an empty parking lot or stretch of road and progressively brake harder and harder from faster and faster speeds. Even go so far as to do "emergency lane change" maneuver's at about 45MPH... then do it harder... then do it harder again. It's important to know how the rig will react BEFORE you are in that situation for real.