First: You may have been scammed. Protect yourself.

SPC isn't available for 1.7.10. I have no idea where you got it from, and you should be suspicious because the only reason for a download site to claim it works with 1.7.10 is for nefarious purposes. The mention of automatically downloading 1.7.10.Mods.jar and then waiting for you to press Play again is especially suspicious, since there is no legitimate reason for a .jar file to have that name, and .jar files can contain code that can do anything it wants to your comptuer. Anything. It's probably malicious, and you should nuke that profile and its related folders immediately and start fresh.

Perhaps run a virus scanner and change your Minecraft password. Consider pursuing any other security measure you can think of that are appropriate after accidentally handing the keys to your computer to a masked stranger.

Copying and pasting your building

That alarm out of the way and security holes investigated, if you're just trying to get WorldEdit commands to do some block copy-pasting, you're in luck and don't need to install SPC.

You can get the WorldEdit Wrapper for 1.7.10, which will give you the necessary commands, and is installed just by placing it in the mods folder. It depends on LiteLoader (not Forge!) before it will load though, but it's an easy install.

But wait, how do I know those links aren't scams too?

To tie this to the first section, carefully note where those links I'm giving you lead: they're to minecraftforum.net (no hyphen! that one's a fake!), one of the few reputable locations to find mods for download (the others being planetminecraft.com and curse.com)?—?because that's where the actual people who make Minecraft mods advertise them.

Scammers are all over Minecraft like brown on toast, and have filled Google's search results with all kinds of tempting-looking download offers, often bundled with malware, viruses, and other nasties. Or just trying to scam a non-functional download to make some advertising money off you. (Scammers vary in their degree of scumminess.)

Never download a mod from a site you don't know and trust.

I believe the latest version of SPC is only available for 1.6.2, and the automated launcher is only available for 1.5 or older. You shouldn't need Forge at all to install it, in either case- the manual installation instructions for 1.6 don't say anything about Forge. WorldEdit.jar should go in .minecraft/bin, rather than .minecraft/mods.

Are you sure you downloaded a legitimate version of SPC? Could you provide a link to where you downloaded it?