How can one parent be enough?

How can one person be enough to help a child not feel the loss of one parent not being here? This is the question I am struggling with tonight.
My husband and I have known for awhile that Little L has some abandonment issues, but they haven't been too severe, that is until tonight.
Today started out good. Little L was so cute on the way to daycare, just chatting up a storm and Baby E was cooing in her carseat. Neither one gave a hoot that I was leaving them at daycare. I picked them both up after school and again both still in a good mood. Half way home Little L just starts crying. I don't mean the whining that he does sometimes, I mean flat out crying with big ole tears. I asked him what was wrong and all he could tell me was "dada dada" over and over again. As my heart is breaking for him, I reminded him that daddy loves him and misses him, that he's "playing army" (that's what we call it for him to understand what is going on) and will be home when his job is done. All he did was nod at that and continue to pout and sniff. We made it home finally, he watched a little sprout, played with his trains while I fed Baby E and made dinner. He had a melt down when the TV was turned off, which resulted in a time out when his melt down turned into a fit. Finally he calmed down, we play some more, almost have another fit, when I convince him it's bath time. He ran into his room to climb up on the crib and wake Baby E (for some reason he LOVES doing this) and we all went into the bathroom for bath time. He played great in the tub, pouring water over his own head and playing with his duckies. We're doing good after bath time, he got a cup of milk and a few more minutes of sprout while I fed Baby E her bed time bottle. Finally it's time for bed. He grabs his blankie, his cup and toddles to our bedroom, where he proceeds to get up into our bed (yes he falls asleep in our bed, then is transferred to his own bed when I'm ready to finally go to sleep, I know it's weird, but it works for us at the moment). I tell him I love him, daddy loves him and it's night night time and sweet dreams. I turn off the light and come back out into the living room and I'm reading a book when he starts calling for me. I tell him I love him and good night from the living room and then proceed to stop talking to him. He continues to call.......finally he just starts sobbing. I walk in there remind him that I love him, daddy loves him and that it's night night time. He has cried so hard he has the hiccups. I leave again and the sobbing starts again. We are now at the point where he almost makes himself sick because he's crying so hard. My heart is breaking for him, so I go back in and rock him until he calms down. He finally lays back in our bed and he proceeds to pull on my arm until I lay down next to him. He wraps his little arms around my neck and buries his face underneath my head, where he finally falls asleep. I don't know, maybe I was wrong to go back in the room and I should have let him cry himself to sleep. But tonights crying was different from his normal fits he throws when he doesn't want to go to bed.
I have no idea what brought all of this on for him tonight. Today started off like any normal day. Nothing has really changed, other than my dad coming to visit for a few days over spring break. But he's gone to bed great three nights since my dad left.
I just don't know what to do, I want to be a good mom and I want to be enough for him so he doesn't feel his daddy's absence. I know he misses his daddy, they are like two peas in a pod when they are together, but how do you get a 2 1/2 year old to understand that daddy didn't leave because he wanted to, but he had to go because of his job? How can one parent keep their child from hurting and be enough for them until daddy is home again? I just wish I knew.