A There are a number of options for neck tightening, many of which you mentioned, such as kybella, coolsculpting, body tite, and some others, but the tried and true best way to do it is via liposuction. This will remove the majority of the excess fat and get your neck as tight as possible with given one’s anatomy.
Lipo is the best “one and done” option to address your neck. We usually charge about 4800 for neck liposuction so it would be within your budget.
Hope this helps!