Oh please, Kit, go buy a digital thermometer. They are very inexpensive now at discount stores. Look in the kitchen gadget area.
Your wrist is not an accurate measurement of a baby bird's food temp. It absolutely must be within a certain temp range or you will either burn the crop or they cannot digest the food because it's too cool. Cool food causes crop impaction which can kill a baby. It hardens up and will not digest, so new fresh food cannot get into the crop.
The air pocket could be caused by an air pocket fed to them in a syringe or a bubble in a spoonful. Use a clean toothpick to break any bubbles in a spoonful. Pull the food backwards into a syringe and tap it with your fingers to release any bubbles in a syringe before feeding. If another bubble forms, clear it again before feeding.
The crop needs to be empty before the next feeding. Parent birds do feed when the crop is not completely empty but they know what they are doing and we don't.
I think with your work schedule you can't continue feeding the next clutches of babies. You need to be there every two hours day and night in the very early days to keep them alive and healthy.
Please read that article I linked in the other message. It will help you.
Annie