I think the tree looks pretty healthy, but as you mentioned, when you got it, health was pretty weak. Going slow may be a good idea. If you leave a good scattering of old needles, when you candle prune in June, say of 2017, or 2018, you can go back 2 or sometimes 3 years, if you still have some older needles on the section you prune back to.
I've had many JBP failures, few successes, most failures were thinking a JBP was 'healthy' and ready, when it wasn't strong enough. Right now my oldest JBP has been with me less than 5 years, started over so to speak. So not sure you should follow my suggestions or not.
I like Adair's thoughts toward final design. Second trunk being 2/3rds height of first.