To go with siblings, I'd say Noah or Maddox. I wanted to say Landon, but the -lan of Rylan and the Lan- of Landon might be too much. Especially if you say them in that order. My favorite, though, is Grant.
I agree with you on that one. I tried to list names that I feel are similar to your current kids' names. My style is different so this is a bit hard for me. Did you like any of the ones I listed? (You've probably seen them all a million times!)
I like those 3 for you, as well. Did he totally veto them? What names DOES he like?
My fav is Ezra, but the one that I think would fit well with the siblings would be Noah. Landon and Rhys are too similar to the other kids' names. Maddox always feels a bit over-the-top to me, and has some bad connotations... So, you're down to Ezra, Grant and Noah. Ezra is an old-fashioned, Biblical name. Grant is quite classic... Noah is a trendy, Biblical name. The other names are trendier... so that brings you to Noah... Asher and Finn would both go nicely...
Spencer, Tucker, Tate, Nolan, Kai, Everett, Emmett, Jude, Jasper, Zane, Xavier, Oliver, Oskar, Owen, Devin, Blaine, Blaise, Forrest, Griffin, Harrison, Lachlan, Greyson, Grey, Mason, Orion, Tiernan, Talon, Max, Jett, Soren, Tanner, Easton, Weston, Wyatt, Bridger, Archer, Wilder, Walker, Zachary, Finley, Gage
If your husband is not cooperating in choosing a name, I'd suggest picking out 2-3 combos that you really like, his opinions aside. Don't bring names up at all for a while. If he asks, tell him that you've already chosen since he didn't give you much input. He'll either go with what you chose, or start contributing. Either way, it may be a solution to solving this naming crisis!
I still like Grant, Asher, Finn/Finley and Heath. I hope you can decide soon!