I really love Shay & Kenzee! And Jace Jack sounds cool together... & i def think very masculine! Remind me why you can't use Jack as the first name? I think from one of your threads i remember you had a reason.... but it seems "Jack" is the one name you've been sure of all along!
Some random suggestions (hope one jumps out at you & screams "this is it!":
Kai, Tristan, Ryan, Rylan, Keegan, Kian, Finley, Riley, Chase, Cole, Colton, Brent, Brett, Scott, Connor, Christian, Noah, Isaac, Isaiah, Elijah, Jamie, Kyler, Tyler, Hunter, Marc, Rocco, Gabriel, Luke, Andrew (Drew), Kade, Kaiden, Braedyn, Carter, Carson, Archie, Oliver, Oscar, Henry, Blaze (Blaise), Parker, Presley, Preston, Owen, Logan, Liam, Leo, Orian, Saige, Collin, Casey, Toby, Nico, Dominic, Kaleb, Donavan, Declan, Shane, Seth, Sebastian, Alex, Dylan, Gage, Jordan, Justin, Brandon, Bradley, Benjamin, Zander, Zaylen, Chesley, Charlie, Chance, Loki, Levi, Peyton, Harvey, Garette, Jackson, Zachary, Cody
Oh & by the way... i think you should give your baby your last name. I broke up with my son's father when i was pregnant too & i am so greatful i decided to give him my last name. I would hate to fill out paperwork (insurance, doctor's office, school, etc) and for us to have different last names. Plus i'm proud to carry on my family name.