First off, spring is not the right time to do this. Fall is ideal. However, you are in WI and if your summers aren't too hot you might be fine. Normally, new grass dies during the heat of summer so don't be shocked if you have to do this again in the fall.

It is normal for some areas not to come in and others to come in thick. Overall the things you are seeing and your questions are normal. The risk of over watering is fungus, the risk of underwatering is lack of germination. If the soil is still a little damp when you go to water again then you are fine.

If the netting is biodegradable then I'd leave it where it is. Pulling it up will disturb the new grass.

Walk on the seedlings only if you have to. Just use common sense.

What kind of seed is it? If it contains KBG (Kentucky Bluegrass) then you might have to water longer than you think. It takes about 3 weeks for KBG to germinate. Check the bag.

If you want to overseed you should use the same seed you originally put down. I'd skip the Scotts as it is probably expensive. DO NOT put down too much seed. Each seed is capable of growing into quite a sizeable plant and you do not need to have a thick lush looking lawn just after everything germinates.

Sounds like you are doing fine. Just be aware you might be doing it again at the end of August.

Get the name of the landscapers so you can be sure to never use them in the future. The big mistake was putting down a netting that needs to pull up. That will inevitably pull up new grass.

1. Yes it is normal...when the landscapers didn't do a great job of applying evenly. But sometimes it happens anyway.
2. Freezing temps should not hurt anything. Again, not ideal, but not a huge problem. You have other problems much worse.
3. You don't want to wash away the seed, and you don't want soggy soil. You do want the seed to be continuously moist for 2-3 weeks.
4. Walk on it.
5. Return the new seed. Pull up the plastic netting, gently, the sooner the better. Mother Nature almost never used plastic netting when She reseeds.

As Daniel mentioned, now is not the best time to be seeding, but in WI you will likely not have the problems most of us have (weeds and summer die off). The alternative was to have weeds all summer. Based on what the landscaper has demonstrated, it is unlikely he killed the weeds prior to seeding. Having said that, since you had no growth for so long, it could be he did kill the weeds. They usually pop up very early in the daily watering process.

If you can find the seed they used, that would help to determine what the lawn will look like. Kentucky bluegrass spreads nicely without having to reseed every year. Fescue and rye do not have the spreading feature, so they often need to be reseeded in the fall.

When you get 80% germination (use your judgement on that), then you can start backing off on the watering schedule. Once the lawn is established (next spring), you will be watering deeply and infrequently. Deeply means 1 inch all at one time. The frequency depends on air temperature, so in your area you will likely water every other week for most of the year. Search this forum for more on that.

Your next question will be, when can I mow? Set your mower to the highest setting and mow when the grass is about 5 inches high.

Are you interested in organic fertilizers? I've been using organic only since 2002. It works great, very safe for the grass, and safe for people and pets. Milorganite is the big one for the WI area (duh), but there are others which I prefer. You can apply organic now. If you prefer something like Scott's, then wait until the end of next month or early June.

If someone tries to sell you weed n feed, ignore them. That is one of those 'too good to be true' products. It can work for some people, but for beginners, it almost never works. Fertilizer goes down in late May and herbicide goes on in April. Applying both at one time goofs up the timing for either/both.