The biggest hill I've cranked up is a 2.5km, 9.5% grade in CA (peaking at 14.9%, according to Strava), using a 32T ring and a 27T cog on my Bianchi. I was well, well under 10mph (well under 10 km/h, even), and would gladly have taken an extra cog as I hit the steep bits... or as I ran out of steam near the top.
On the other hand, I'm riding mostly flat lands now and you could almost eat off off my 34T and 30T cogs I use them so rarely. There's one 9.4% gradient on my normal route, but it's short enough that I can power over it.
My opinion to the OP is that if he's looking for close ratios and hill climbing ability, a sub-compact crank is the way to go. A 48/32 mated to an 11-32 would give 1:1, an 11-34 would do better- or as others have noted, going GRX would do even better than that. Alternatively, an 11-34 cassette when he's visiting the girlfriend, and swap in a SRAM PG-1170 11-28 for the close-ratio goodness he wants (single tooth differences between 11-17). Or better yet, have the GF visit him.