Been rooting for you on your journey and thought I'd check your blog to see how you were doing and then you posted today! Thanks for update though sorry its not same ol' no news is good news
T seems to have always been a very independent spirit which I would imagine is why you're attracted to her. Sorry to hear it may be 'fading away' or it may well just be a phase; her focus is needed elsewhere so attentions are less on you.
Not everyone may agree but in this case I'm going with the "put your mask on before your loved one" thinking: do what's best for you then for T. If you are healthy, happy, strong you have more love/attention to give to others. T doesn't need as much from you now so give her a love note, send her some encouragement, talk on the phone, whatever AND pursue a relationship that will fulfill more of the attention you prefer.
Its not wrong or unfair to T to pursue another relationship even if she's going through a rough time. If/when she needs more than a reminder you love her then she seems plenty confident enough to let you know and/or keep asking her what she wants, what works for her now. She's also had multiple people vying for her attention and you've both dealt with that, setting relationship parameters and asking for what you want. You like/crave attention, seems T has always been very independent and doesn't associate love & attention the same way you do, so getting attention elsewhere is win/win. 'Tis part of the beauty of poly.
Also, give my best to K! She sounds so remarkable and generous and truly coming from love. Think there'd be a lot more harmonious marriages out there if people could be more like her
And kudos to you getting through the SCUBA thing. I would've suggested you find something else you two can enjoy together and let her do the SCUBA on her own or with another friend. That's brave, intense; AWESOME, Dude!