I’d start by saying looking at the benefits of your respective pensions. As your NHS pension may have more generous benefits than his pension. And factor that in alongside the tax relief.
So the tax relief may “buy” him more pension, but what you receive come pension time is also a factor.
Also give consideration to things like the stability of the pension, how many years you have to contribute before receiving it, that kind of thing.
You can get tax relief on pension when you are not working, it’s all annualised. You can even get tax relief on pension contributions in a year when you pay no tax at at all, up to a contribution of £2,880 (or £3,500 when tax is added).
Also bear in mind that you can back date contributions with respect to tax relief for up to three years I think, as long as in the future year you make a back dated payment in you have made your maximum eligible pension contribution in that year.
Those two features of course also depend on what your schemes allow. But it’s possible that you could make payments to your pension fund whilst you’re between posts and next year (or the year after etc) max out his contribution in that year and then make back dated payments to his fund.
DP took a huge temporary salary cut in 2020 to help with company cash flow made up the pension contribution the following year after the company basically gave everyone bonuses amounting to what they’d sacrificed to keep the company going (and then some as a thank you).
I’m chronically ill and not working so every year we make a contribution to a private pension for me and tax is reimbursed up to the limit previously mentioned. (This also applies to people who are in work but due to being part-time etc don’t pay £620 pa in tax).
It’s bear in mind that if you were to split, the value of pensions would be taken into account as assets in the division. So that leads you back to probably comparing the value (by outcome) of what you “buy” with your contribution.
I do understand though that there may also be concerns regarding different incomes in retirement if you stay together if you’re aren’t just pooling income equitably.
Anyway, hope this helps.