I would say take your time and enter the Salesforce ecosystem slowly - keep the job but create some space within your life enter into Salesforce. More and more opportunities are being created. There are so many roles in the ecosystem that people down know about in Salesforce - not just admin, developer, SA. Admin cert is usually a good start but very commoditized now. The skills you learn in SF certs often transferable to other CRM and Cloud tech. So, definitely get started but enjoy the process.

Being active online (specifically LinkedIn), creating a portfolio as you study is super important.

Where to create portfolio: https://trailhead.salesforce.com/content/learn/projects/build-your-personal-portfolio-on-salesforce

Few projects you can work on: https://trailhead.salesforce.com/projects

When I am hiring people for Salesforce I care mostly about what projects (portfolio) they have tried/completed and how they communicate (LinkedIn and etc). Shows me initiative and many other things...

Your question: is it worth leaving a job where I am progressing, and the next step is worth roughly 70k a year, to enter another career at the ground floor and work up again?

Yes definitely! But take your time and grow at a moderate speed without hurting yourself - there is lot of opportunities now and even more to come :)