I think 1 is ONODRIM, but I don't get 'conjunctionless,' unless it's 'NO OR' ... but that would take the R from RIM.
2. The great SEA, which sounds like see?
...
Maybe OSSIRIAND for the password?
I'd say DERNHELM for the last one ... four letters of GARDEN plus HELM, but we don't hear anything about Eowyn's offspring.
Perhaps there's another Dernhelm?
3. Silly Mary ill gives SILMARIL if you make the two double L's single and take out the Y's.