Need a little help with 7Zip

Videos and photos are already compressed, so you wouldn't gain anything if you compress them (unless the pics are in raw format and the videos in ts)

Short and undocumented answer: zipping media files is 99% useless. It can be useful to put many media files in a stand-alone zip (or other compressed format), in this case I only use the compression setting "none"...

to give you an idea:
2.350 jpg files ~1gb
files zipped (zip ultra compression)

compression is mostly useless (unless it's an uncompressed file like photoshop PSD), do like m0l0 said if you just want everything in a single file.

Don't rush, see if you can borrow a portable HD from a friend so you can make a secure backup.

As already stated by some, compressing photos and videos is useless. The only exception would be, if they aren't already in a compressed format. However it does make sense to make an archive, if you have a huge number of relatively small files, because copying a single large file instead would take much less time (especially useful, if you have to back it up in multiple places). Just make sure to select "None" as the compression level. If you go this route, you should also consider adding a recovery record to the archive as well.

pcloud.com provides 10gb free storage but you can up that to 20gb by doing some simple stuff like liking them on fb or subscribing with you email for newsletters or even completing their tutorial

Why so hard way? Use MS OneDrive, there are 15GB free space for your files already. (If you have win8 then you should be registered already. if not you can do it here, since you like ref links :D or here, if you don't)

AFAIK, Google Photos gives you unlimited cloud storage for your photos, if 16MP or lower (the files do get compressed though (but if you're not a photograph or don't work in image design won't even notice) , but the resolution isn't reduced). Also Flickr gives you 1000GB for your photos for free (original files don't get compressed, web-shared files might; but again, you won't notice any difference without studying them closely).

Both Google and amazon offer unlimited photo storage place. And they pretty much consider any JPEG and RAW file with a photo header photographs.
If you use a simple cloud storage, do what was advised earlier, and compress them with none (or "store") level. One large file is a lot easier to handle than several small ones for backup purposes. (This is why many programs and games use some non-compressing container format to store their assets.)