New construction home, loose foundation anchor nuts

As a former construction estimator, I would suggest that you get in touch with the contractor sales department at a building supplies store in the area in which you're considering building. Quite often the estimators there will have a ballpark "per-square-foot" price for materials, and may have an idea of a ballpark price for labour, too. They can probably refer you to reputable builders as well.

That said, there are really far too many variables for a ballpark estimate like that to be at all useful. You can get a house to lock-up fairly cheaply, but it's the finishing work that's really going to determine the end cost. The cost of a beautiful metal tile roof is going to be a lot more than 20-year asphalt shingles, and the cost of vinyl siding is going to be a lot less than stone, as examples.

To get any kind of accuracy in an estimate, you're going to need to have a set of plans and you'll need to decide what exactly you want in terms of finishing, land, appliances, etc. Anything shy of that is really just going to be pulling numbers out of thin air.

The anchor bolts need to go well into the block, preferably at least 8" in. You should place the anchor bolts in the head joints of the 4" solid run. No need to drill holes in the solid block. Worst case cut the solid block where you need to and set the bolt in the joint created in cut block. They should coincide in a hollow place in the rows of block below often enough to work in a bolt about every 4' maybe slightly more if need be depending on your seismic area. Masonry supply houses carry anchor bolts 16" or 24" long. In my opinion, you should use a minimum of 16", again, depending on your seismic area. There are other types of clips that will do the same as a anchor bolt.