We've had Cruiser a week tomorrow. He's eating good now and playing a lot. He's much better. He's doing good with the potty training for the most part. He sleeps good at night. Now on to things we haven't started:
How often should I give him a bath? He had one last Thursday at the breeder's. I have brushed in almost everyday but I have given him a bath.
I give Bear a bath once a week. It really depends on your Yorkie's skin & if it gets dry really quickly. If it gets dry quickly then you shouldn't bathe him too often. Also, you shouldn't brush his hair when it is dry because this can damage the hair. Either use a conditioning spray on it first & then brush it, or just brush it after his bath.
How often do his ears need to be cleaned?
I really don't know, lol.
When should I start brushing his teeth? Do you do it everyday?
You should start brushing his teeth as soon as possible. Yes, I brush his teeth every day.
When can he start walking on a leash? We haven't attempted to put the harness on him yet.
It depends on how old your Yorkie is. You have to wait until he has all of his shots before you can take him on walks. First I would put on the harness & let him get used to it. Put it on for short periods of time, like fifteen minutes at a time & then take it off. Gradually increase the time that he is wearing it. After he is used to the harness, put the leash on him & let him walk around with it dragging after him. I would do that for about a week so that he gets used to having a leash on him. It takes awhile sometimes for them to get used to being walked, so be patient with him & he will get it eventually 
Some pick it up quickly & others take awhile to get used to it.
What age is a good age to take him to puppy kindergarten? Is Petsmart or Petco okay for this?
I would say after he has had all of his shots is a good time to go. A lot of people on here do not like Petsmart or Petco puppy classes, but it really does depend on the instructor. See if you can sit in on one of the classes. Observe how the instructor interacts with the dogs & their owners. Talk to the instructor & ask her about her/his classes & how he/she runs them. Talk to other people who are in the class & ask them if they like the class.
With all the problems with had with the vaccines and the emergency vet, etc., I am thinking of switching vets already. Is Banfield (attached to Petsmart) okay? They have a good plan cost wise.
I have no idea. Remember that cheaper isn't necessarily the way to go. There are some vets out there who are amazing who don't charge a lot, but to be honest, you should be more worried about the quality of your vet instead of how much they charge you. I would give the Banfield vet a try & if you don't like them then switch to a different vet.
I am leary about giving him the heartworm tablet that the vet gave us because the reaction he had to the vaccines. Also, he has to go on a medicine because his stool sample came back positive for giardi (spelling?). She said it's a powder to mix with the food and we should start it next week. Should I wait to give him the heartworm tablet the following week? The breeder suggested only giving him half the tablet. What do you think?
In my opinion, I believe that you should give him the full amount of the heartworm tablet. They are supposed to take the entire thing, not part of it, so I would advise you to give your Yorkie the whole thing. I give my Yorkie the entire tablet & he is fine with it. I know that you are worried about him because of his reactions to the vaccines, but the heartworm medication isn't the same thing as a vaccine, so I'm thinking that he will be fine taking the whole tablet. If you are really worried about it then I would monitor him for twenty-four hours to make sure that he doesn't get sick from taking the heartworm medicine.
How harmful would bird seed be to him? I posted before that we have pet cockatiels. They are messy and there's always a little seed on the floor. Well, being the little cruiser he is, he is always cruising around and trying to eat the seed. I stop him, of course, but I'm sure he's already eaten a couple of seeds. We will do a better job of sweeping and vacuuming, but we're never going to get it all. Hopefully it's not too terrible for him if he ingests a few seeds.
I don't have birds, so I don't know 
What do you do about cords? He keeps trying to chew the cords to the lamps in the living room. There is no light fixture in the ceiling so we have to have the lamps. I keep distracting him from them but he gravitates back there.
Try spraying bitter apple on them. Some dogs don't like the way that that tastes & they won't chew on cords & such if they have been sprayed with bitter apple. I believe that you can buy the bitter apple spray at places like Petco & Petsmart.
I guess that's enough for now! I really appreciate everyone's helpful comments.