Got Two Heroes With Weird IV's. What Should I do With Them?

+attack on a nowi is decent, but not that great since she has a speed bane. Regardless, since speed doesn't affect her survivalists much, that nowi is pretty good. The ephraim, +speed is good and -attack still keeps him at 48 with siegmund. He will be very helpful for you. Level up both and maybe wait for a better nowi to invest in unless you are free to play. If so, upgrade whoever you can. Yes have a hector with terrible IVs (-def +res) but he is still overpowered. Never under estimate a unit with bad ivs

If you have a 4 star seth you could try fortress Def on ephraim. Kind of a troll skill but makes his defense
D I S G U S T I N G. Pair this with bonfire or default moonbow and either quick riposte or lance breaker.
37 defense with 29 speed is like an armored blue unit

-Atk isnt the end of the world, especially if you want to use him as a buffing unit for blade tome users.

Your Nowi isn't that bad. -Spd isn't great, but getting doubled doesn't mean that much if you're not taking damage. I'd use Triangle Adept and Quick Riposte, using her to bait red units and double on the counter attack.