See Help/Installing the Lord of the Rings Mod. Also this is a really old thread, you should open a new one for other requests.
My guess is that "ID is already registered: 186". Looks like a mod conflict. If you read down the stacktrace a ways, there's something about battle towers in there, so my guess is that it's battle towers that's trying to re-register that ID. Removing battle towers might fix, or you could work through removing other mods to see what else works.
You can unpack the mod file as a zip (.jar is just a .zip with a different extension to make it obvious what it is). There's a bunch of files in there, you can find the map and change it.
Idk about spiders vs horses, you could check the wiki pages for each, I bet the average speed values are there. It's also possible that they're defined in the mod file someplace, but you'll need a java decompiler to read them.
With the day night cycle presumably.
I got a response on the Veloren discord:
It looks like they have a preset size for worlds though, and it's not proceedurally generated throughout gameplay, so that's a sticking point.
There was something I saw I saw with Veloren about seeing far in a generated voxel world, but I wasn't really able to find any more interesting info, I'd be interested to see how they do it in these screenies: https://veloren.net/devblog-56/
Tbh the thing that costs so much to render MC worlds is that you have to iterate over every block and do a reasonably expensive set of calculations in order to be able to render, if one were able to reduce the cost of that iteration (by say, iterating over every other block, or every third, depending on distance), you could theoretically extend render distances really far. I might do some looking into forge API and just see if I can wrap my head around how rendering works.
Also Windows 7 is unsupported, connecting it to the internet is pretty hazardous as is. You should see if you can get a newer machine.
Your crash is probably just java running out of memory:
The following is a tutorial on allocating memory for minecraft using the LOTR mod. Please note that allocating the recommended amount of memory will require a 64-bit version of java. Choose your launcher below.
Old Vanilla Launcher
New Vanilla Launcher
To allocate more memory for minecraft using the newer edition of the vanilla launcher, click on
Launch Options, located on the right side of the menu bar. Click on the profile you intend to add more RAM for, and locate the box entitled JVM Arguments. Click the gray toggle to enable arguments for this profile. In the box, put -Xmx2G or -Xmx2048M. The recommended amount of memory for LOTR is 2G, but if you are using a high resolution texture pack you should allocate more. Likewise, if your computer is limited on memory, you may want to allocate less to be sure that your operating system and other programs have enough memory.Technic Launcher
MultiMC
Userpage link is broken, I fixed the code for you:
[[File:SwordArnorian.png]] '''[[User:Walking Ranger|<font color="#0B3B0B">Walking Ranger</font><font color="#0B3B0B"> of the Dūnedain </font>]]'''[[File:Ranger_Bow.png]] <sup>[[Message_Wall:Walking Ranger|<font color="#0B3B0B">Join my Adventure! </font>]]</sup>