How to leverage an offer from a direct competitor if I found out I am a valued team member when I resigned?

Hey everyone,

After I told my boss I want to leave in a month's time, he was extremely dissappointed - it turns out I was considered a valuable team member and not as easily replaceable as I had thought (imposter syndrome). He did not want me to hand in a resignation, based on advice on WSO I did not tell where I am going . It is our #1 competitor.

He did not offer me more money because I based the reason I am leaving on the fact that I am not growing, tasks are boring, not learning as much, etc. Now I think I should have mentioned comp as well.

There are several things I can do but I am not sure:

(1) tell my boss that I may be willing to stay but cannot do it with the same conditions that I currently have - imply that I may have an offer from a competitor (he really does NOT want that, I know too much) and try to get more money. this would be hardballing and be extremely tough to pull off

(2) fuck it, burn some bridges, go to a competitor (although salary is a bit better, it is less than I think I deserve, but these are 2 best options locally)

TL;DR Try to get more money and help with transfer at current place by implying that they are screwed if I leave or fuck it, make some enemies and move on from the bad situation?