Actually, I think I've maneuvered myself into a rather strong position.

I have an exciting and fun job on the cards, that I've been engaged with for a number of weeks. I'm technically getting to benefit from a trial period of said job since I'm doing it in my spare time for the next four weeks. This job nets me a 15% increase on top of my current salary, after three months.

If for whatever reason, that doesn't work out over the next couple of weeks and I either hate it or decide I don't like it (unlikely, but still a possibility), I have a 30% salary increase with my current employer to fall back on. That's pretty much a win-win.

You might think "Wait, why is 30% a fallback over 15%? You mad bro?"

Well, it's like this; I either take a 15% increase and do a fun, flexible job or take a 30% increase for a job chasing people for money, that I wouldn't enjoy as much.

It's a dilemma, but an interesting dilemma.