So Windmill hill is in line to Avebury
This is one of Europe's largest stone circles
There were originally 98 sarsen standing stones, some weighing in excess of 40 tons.
At the risk of stating the obvious, any two places are always in line with each other. I am saying that Windmill Hill is in line with a right angle to an axis that is a bisector of one of the arcs I found describing the plan of Avebury. I don't think it is enough evidence to securely lock the two features together, but the Archaeocosmologists of greater ability than I (not difficult) are looking at a lunar alignment that might add weight. These depend on viewpoints, foresights and backsights, so without knowing these we can only talk of possibilities. You can see Windmill Hill clearly on the horizon from The Cove within the northern inner circle.
As for the number of stones, estimates are difficult because of the missing portions and the irregularity of the stones themselves in size and shape. When Keiller re-erected the stones, and it really was a sorry sight/site before then, he re-erected stones with their flattest side outward where it was not obvious how they once stood. So they look like a more regular set of teeth than once they might have.
Keiller took detailed notes of the excavations he made, however when he came to clear the banks of the trees, he blew them up with dynamite. Not exactly the technique that an archaeologist might use today.
Current estimates, as well as Stukeley's in the early 1700s, suggest about 100 stones in the outer circle.
What has come out of the recent Papworth survey is that there are anomalies in spacing at two places. One is either side of the only existing stone in the north east sector. The stones are much closer together either side of this stone. There is a similar situation in the south east, where three buried stones lie closer together. I think it is something like 9 metres apart rather than the usual gap of about 15 metres. This puts extrapolated estimates out and we might have 101 or 102 stones. I doubt we can ever know for sure, but 98 is too conservative.
South of the road at the eastern entrance is a triangular area where once stood a house. You can see it on Stukeley's plan above. This fenced off plot is the only part still left in private hands, it's owned by an old lady in the village and she will not allow access to it under any circumstances. It has never been excavated and it may well contain two buried stones - maybe even an impressive entrance stone. The geophysical survey worked to the edge of it and strongly suspect a buried stone to the south, there's a resistance anomaly, but the change in level here, dense undergrowth and lack of access made further investigation impossible on that occasion.
Another thing to remember about Avebury is that the southern entrance has moved. When the road was widened in the 1800s to the west, material was taken from the bank to the west, where a big depression and scar is seen today. The chalk was used to level the road. Where the trees now stand today at the east of this entrance was built up to the top of the bank and is thus modern and misleading. The break in the ditch still shows where the original entrance really is, facing the two existing entrance stones.
There existed a huge stone to the west of this entrance, at the edge of the old road, which was an obstruction. It was broken up and taken away in I think 23 cartloads but don't quote me on that. Some say this huge stone was the left one of the entrance pair and the left one we see today is actually the right. Personally I don't buy it.