How to get my dog to stop barking when I go upstairs to bed?

I have a 4 month old Chihuahua/Dachsund mix Oscar who REALLY likes me. I know he has a separation anxiety problem that we are working on but for now we are using a gate to keep the dogs in the kitchen- don't worry, the kitchen is enough room for them. They have a crate but haven't been introduced to it yet completely. Whenever I put Oscar in his crate he cries and bites on the bars stresses himself out.Just by going to the other side of the gate he stares at me and barks. I tried using my robe that smells like me on their rug and that worked one night I also put a moist towel in their crate and that also worked but just in case it won't last I need more ideas. HINT: I cannot give them their Kong because I only have one and they will fight over it all night and when they fight, they bark!