I am wondering whether you think it is worth it to try a bootcamp if this next onsite doesn't go my way? I'm desperate to leave my job, but I've heard mixed things about bootcamps.
You need to debug your job hunt. Conventional wisdom is that you need to think only about the stage you are getting stuck: that is, if you ratio of applications to interviews is bad (it is) you need to improve your resume, CV, cover letters, who you apply to, etc.
The level of success you're describing in the interview process is not abysmal but I can tell you are worried about it and would say you also need to work on "presentation of self".
Most of the bootcamps out there are: (i) applications programming in Javascript or (ii) data science with Python. These don't work miracles but they might fill in a gap if there really is a gap.
What kind of jobs are you looking for?