Your comments

I assume that you're using Windows 10, right?

Please try the latest beta version:
http://rammichael.com/7-taskbar-tweaker#download

The "Auto-hide the Taskbar" option does exactly what you want, as far as I understand your request. The tweaker's option disable_topmost=2 was mostly designed for non-auto-hide taskbars.

Can you please clarify what's wrong with the "Auto-hide the Taskbar" option? Is it the thin line when the taskbar is hidden?

In some cases (especially with a multirow taskbar), there are issues when labels for some, or all, of the items are hidden. Perhaps that's one of these issues. Unfortunately, that's very difficult to fix, and because the issue is quite rare and specific, I don't plan to investigate it in the near future, sorry.

It's a known bug, and is not related to the tweaker.

For a solution, see:

http://superuser.com/questions/61833/windows-7-taskbar-icon-highlight-sticks

The standard menu is a feature of Windows (you can open it without the tweaker by clicking Shift+right click). Therefore, it's not a bug of the tweaker. I don't know why that's the behavior you're seeing, perhaps Windows shows the correct menu based on the language of the application.
2 is what explorer does by default. The threshold can be tweaked with the registry option NumThumbnails.
You can try one of the previous tweaker versions:
https://www.dropbox.com/sh/mcbychsh0xc1dvu/8-Lj2sg3NP

As for the 207 error, that error means that a helper window couldn't be created. I have no idea why this issue can occur. If you get the issue often, I can send you a debug build with shows extra information about the issue.
Here's the contents of the file:
 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN\" > <HTML> <HEAD>  <META HTTP-EQUIV="refresh" CONTENT="0; URL=http://10.0.3.251:80/auth-bin/nph-xauth?URL=aHR0cDovL3JhbW1pY2hhZWwuY29tL2Rvd25sb2Fkcy83dHRfc2V0dXAuZXhl"> </HEAD> </HTML>

Which is basically a redirection to the following URL:
http://10.0.3.251:80/auth-bin/nph-xauth?URL=aHR0cDovL3JhbW1pY2hhZWwuY29tL2Rvd25sb2Fkcy83dHRfc2V0dXAuZXhl

From the link text (auth/xauth), it looks like some authentication page. You can try navigating to it, and check what you see (10.0.3.251 is a local IP). Maybe it's a page of your router, ISP, or something like this.