No way should you be able to set the bars onto the L brackets without help (jacking up the tongue or using the lifting lever). This tells me your hitch head is not set at the correct height and/or angled with the correct number of washers. Best to disassemble, repair or replace parts that need it, and follow instructions for getting proper measurements before reassembling. The previous owner may have had it set right for his tug, but it is not set right for yours.
Without the right amount of pressure between the bars and L brackets, you have little to none anti-sway and weight distribution... might as well leave it off and tow with a plain ball.