The recipe is incomplete. As far as adding nicotine, it depends on your base and how much nic you want. A
juice calculator is often handy for that, and it will allow you to input what your nic base is made of Vg/Pg/mix of the two and will allow you to figure out what final VG/PG percentage is made up of. Depending on the manufacturer, flavors will be PG or VG, but most come in PG, so that's typically taken into account into the mix as well. Percentage of flavoring will be based in PG usually.
I'd agree on reducing the sweetener a bit, and possibly the overall percentage. It has been my experience that underflavoring a bit is far easier than diluting a too strong mix.
Kind of take the recipe as a guide, and then add/remove/diminish what you want/need to. Start small, keep notes, try to fix any failed mixes would be my advice. Honestly. DIY kind of builds on itself, and there's no wrong place to start (other than perhaps, mixing an ideal flavor right out of the gate, and not keeping good enough notes for you to remake it. That's a mistake new DIY flavorers tend to make-- once.)
Best of luck, I hope the mix works out well for you.
Anna