Station wagon with manual transmission - daily driver

I put three car seats in the back of a Mazda Protege5, and the Golf has a roomier rear seat than that Mazda did. It does help to pick relatively compact seats. Later I used Grace Turboboosters because they were relatively narrow.

The Golf SW is pretty much your only option, so luckily it's a very good one.

If you're open to AWD, the Subaru Forester might be a possibility. But the Golf handles much better.

The Mazda3 5-door has very similar interior specs to the Golf Sportwagen and it actually has slightly more interior room overall. The i Grand Touring (2.0L) and s Grand Touring (2.5L) can be had for under $24k (MSRP is $26k+ on the s, but you can buy it for a hair under $24k). Both models are available with the 6-speed manual.

The V60 is likely too new to cost only $15k. 2015 was the first year.

If you meant V70, then 2007 was the last year those were offered with a manual, and reliability will be questionable. Especially for the 300-horsepower R (which would otherwise be very attractive).

2010 was the final year for a manual V50. Nothing special, iffy reliability, and limited cargo space.

An Audi A4 could be a possibility, but a $15k Audi is rarely an inexpensive-to-maintain Audi. Otherwise, it would cost more than $15k. Same for the BMW 3-Series wagon, though I'd have a little more faith in one than in the Audi.

A Saab 9-3 would at least be newer for a given price. It's likely the one you'll be happiest with.

2006 was the last model year for a manual-transmission Mazda6, and 2005 was the last for a manual transmission Legacy GT. So those are likely too old.

In 2009 the Jetta SportWagen was offered with the 2.0T. Reliability concerns with this one as well.

If you decided you didn't need much power, the Elantra Touring could be an option.

Overall, I'm thinking Saab unless you can find a killer deal on a 2015-2016 VW.