Also, my vet told me that with Yorkies it's also better that all their baby teeth are almost all out because they said in this breed that it's not uncommon for the adult teeth coming in process to slow down when neutered or spayed due to the hormone influx.

Of course! Everyone always tells me that Chloe is too big. She is 5lbs... I become a momma bear and get so protective of her just like I do with my human babies!

Definitely wait until he is 6 - 7 months. Then if there are any deciduous teeth, they can be extracted at the same time.
As for leg hiking...I assume you are referring to marking? Here is some information that may help:
Urine Marking by Dogs - Page 1

Moses was neutered at 6 mos, had those baby teeth pulled and has never hiked his leg. He was under 4 lbs. However, he will hold one leg slightly off the ground when he tinkles! He looks pretty prissy when he does that!

Kaji was neutered at 12 months. I didn't have a choice as he didn't come home until his first birthday. He was a marker, but with training he doesn't do that inside anymore, only outside. (1 1/2 years of zero marking!:)) but if it's actual leg lifting you don't like, I think that comes with their personality. I honestly think it's cute when Kaji lifts his leg to pee. I've gotten a little creative with the piddle pads. ;)

As far as when to neuter, listen to Mardelin. The only thing I would add is get him microchipped at the same time of the neuter. (if you were going to microchip your pup)

My vet said to wait until 6 months at the earliest for my boy. My little girl is smaller so 7-7 1/2 months for her. Before I selected a new vet, I asked the vet a lot of questions about how many small dogs he and his partner has worked on. I also asked a lot of questions at the front desk and got referrals from friends before I got my furbabies. My old vet was fine, but they were further from the house - with the heat here I wanted somewhere a little closer to home.

My current vet charges $130 for boys and $150 for girls. My old vet is $365 and $395. They both offer the same service with same features - such as monitor, IV, blood work, etc. Not included is pain medication - which is an extra $8-12 - course I will pay! My new vet fees are similar to my old one for most other services, so I asked why the spay/neuter was so much cheaper. The gal at the front desk laughed and said she had never heard that before. She said they do not charge extra for blood work or monitor or IV's.

One of my old college buddies is vet and said the spay/neuters are a money maker for most vets. He said that responsible dog owners will usually pay whatever the vets charge without question. He mostly charges a flat rate for boys and girls, but offers a tech service - for an extra fee ($50-80) you have one vet tech who is assigned to stay with your pet from the time they get out of surgery until you pick them up. For folks who want this service, they get to meet their vet tech when they drop their pet off. The tech is with them the entire time. Would make me feel better to know someone was with my little ones the entire time.

The local spay and neuter clinic in town is $65 per dog regardless of gender.

Best of luck