Looks to me like you have an older EazLift hitch. There is nothing wrong with that and you should be able to use it with your trailer as long as the spring bars are of the correct size to be able to handle the tongue weight.
Take a look at
this thread for instructions on setting up your hitch. It will tell you, in detail, exactly how to go about it. Your hitch is not set up correctly as you lost 300lbs off the front axle which was moved to the rear axle. So that weight of 3840# includes the 300 moved from the front axle. You need to adjust your WD (take up more chain links) to move that 300lbs back to the front again. This also means that your tongue weight is probably in the 900lb range.
If this link works correctly, it will lead you to my dropbox folder to get the installation manual for a round bar hitch. It is not an EazLift but the instructions are about the same no matter what the brand.
Round bar installation instructions.Barney