Same, so I just gave Lucina most of my stat boosting items. Also, if you really need to, you can use a Second Seal to change a unit to the same class. They go back to level 1, and don't lose any stats, so you can just keep leveling them up to boost their stats.
Honestly, I just took my best unit (Lucina), and paired her up with Chrom because of their high support, and just sent them out against Grima. Meanwhile, I just paired all my other units together and just tried to keep them alive until Grima was killed.
Oh yes, I remember that. Yes, it never fails when a friend is around you pass something. It's happened to me plenty of times XD. Congrats on finishing the level. I hope you like the ending.... nyaaaah I won't spoil ^.^