You’ve posted a lot of inspiration material, but most of all i think you should try to follow the style of this nearby homestead:
This is the new road situation:
If you want to make a crossing over the river, just make it a small ford. There will be a larger bridge crossing that river.
Also note that your farmstead is in the floodplain of said river. So make sure to raise the ground for the houses that you marked in the southeastern corner of the plot. You’re planning to add a lot of stuff, but when building you can also decide against building all of the elements you’ve marked. Sometimes less is more, and will look better. I’ve removed the small path that crossed the river, because it makes a lot more sense if it stays on that side of the river to link up with the road west of it, leading to Edoras.
You can start building on the main world, but expect a lot of involvement from other players. It’s one of the most important areas of Rohan after all.