|I am So Glad my answers were helpful to you, and that Taco and Tequila are getting along better. I'm also glad that Taco was restored to his place and is now getting the proper nutrition. He understands you are alpha, which will make everything so much easier.
So, now he's eating from his own bowl as well as hers. Yup, he's showing dominance. The top dog gets to eat first, then the next lower member in the pack, etc. until everyone has eaten or the food is gone.
Of course, he may be eating more because he's getting more exercise. My Gremlin started eating like a horse after I added Nixie to the household, but she stayed slender, she was burning off calories like crazy playing with her sister. Your vet can help you determine if Taco is getting too heavy, you can tell too. If there's not a nice tuck up behind his ribcage, and or there's padding when you try to feel his ribs, he's getting tubby. Tubby chihuahuas are unhealthy chihuahuas.
If you choose to give them treats, make sure you've finished eating first. Only then can they have a small treat, if they have waited patiently and quietly. No jumping up or barking or they don't get anything.
Give Taco his treat first, he's next in the hierarchy. Then give Tequila her treat, tell Taco "No, you already got yours" if he tries to take it.
Food bowls, same thing. I always keep kibble out but each of my girls has their own bowl. Gremlin used to try to keep Nixie away from both, but I used the same technique. Gremlin would eat first, from her own bowl, I insisted and took Nixie's up if she wouldn't behave. Then Nixie got to eat from her bowl, and I was right there to make sure Gremlin didn't harass her. Since there was still food in Gremlin's bowl, she didn't have to worry about being starved. If she went for Nixie's bowl, I just picked her up and put her in front of her own.
Now that they're both adults (Nixie will be 1 year old on Thanksgiving, Gremlin will be 2 on Halloween), they will eat out of whichever bowl is more convenient or has kibble in it. Gremlin eats from Nixie's if she wants, but Nixie still asks Gremlin if it is OK to eat from Gremlin's dish. One growl, and Nixie goes to her own bowl or comes and gets me to please fill hers.
If you are feeding only at certain times, then give Taco his bowl first. If he eats all of his, put more in until he's full. **
** A lot of people say not to keep food out constantly or give a dog more than the side of the bag says to, but my experience has been that if food is always available, dogs will eat until they are full and stop. This works better with dry food than with wet, semi-moist is the worst and I cannot recommend against it strongly enough. It's junk food, full of sugar to keep it from drying out, and chihuahuas don't need any extra sugar.
If he keeps eating as fast as you put it in, then this isn't an option, give him his food and then that's it. Either way, when he's done, give Tequila hers and put Taco right back in front of his if he makes a try for it. You might end up having to feed them in separate rooms. Just remember, give Taco his food first.
I'm glad you're going to get the book, and do keep in touch, your questions help a lot of other people who maybe don't know what to ask.