Known as "oil canning" this is a common problem with plastic kayaks caused by long term storage or tight loading straps on roof bars.
Luckily you have a minor case and since this isn't a performance boat, the effect is entirely cosmetic. However it can be restored with the application of heat and pressure.
The best heat source is a hot sunny day. ...
Correctly applied silicone of the right grade is a (semi) permanent solution.
Like any other submerged seal it requires regular maintenance and inspection, but if you get a silicone that's designed for continuous submersion in water then it will hold.
Broadly speaking, your steps seem perfectly reasonable. Completing them will leave you with a board with protection and strength.
Your question at the bottom is entirely up to you - if you are likely to bash the nose into rocks or while transporting, then adding more layers will add protection, but personally I wouldn't worry too much. They are pretty robust....