Some excellent advice and perspectives above. This forum does inspire me now and then.
I have to say I think keeping one kite and board is not extravagant. It will provide an important outlet, as well as having symbolic value as an indicator of your retained individuality, sitting alongside the symbols of the sacrifices that you make for the relationship.
Also, seeing a skilled counsellor (and how to find a really good one is itself a journey) to talk through the new arrangements would likely be a very worthwhile move.
Are you familiar with Maslow's hierarchy of needs?
en.wikipedia.org/wiki/Maslow's_hierarchy_of_needs
Whilst it has had its critics, my experience as a people-helper is that it can be a useful tool in thinking about priorities. Taking care of the basic stuff first enables the higher pleasures to be enjoyed more fully, rather than with guilt. In some ways this is common sense, but for myself and some clients it is very useful to map the ways in which we meet our basic needs and those of the people close to us. Is anything missing, either for you and your partner individually, or for the two of you as a unit? Is the distribution of need-meeting equitable? Is it sustainable? Are there needs you haven't acknowledged or addressed so far?
Balance, balance, balance. Keep it dynamic, keep it in process. Check in with yourselves and each other regularly. Have time for closeness, and time for space. Stay present to what's happening in the moment, and new understandings and possibilities are sure to emerge.