An obvious adjective, given the description, is romantic:
A surge of wild romantic pride swept through him.
However, that could be misconstrued as a pride of romance rather than pride of a romantic partner. So, it might not be acceptable.
Another possibility is paired.
From the noun pair:
2 a (2) : a couple in love, engaged, or married
// were a devoted pair
A surge of wild paired pride swept through him.
Again, however, an objection could be raised that this confuses pride being paired with something else (in its more traditional use as a verb), rather than it being his pride in his complement in the pair.
This variation is possible:
A surge of wild pair-pride swept through him.
It's a constructed term, but the meaning is clear—and it's exactly the meaning looked for.
I personally like pair-pride; however, it might not sound completely natural to some people.
If paramour didn't have a negative connotation and it had an adjectival form, it could work. Unfortunately, neither of those things are true.
It could be that there simply isn't an adjective that is completely appropriate in this context.
If not, the only option is to rephrase the sentence.
A surge of wild pride for his romantic partner swept through him.