Deleting Photos, what iCloud saves and how to access things from iCloud and device storage issues
Your question is probably about 5 ones about how things work, so I'll address the elephant in the room.

You need to decide how you want your photos to be stored.


Where do you archive them for long term storage?
How many can you afford to lose?
When and how will you clean up all the photos that come from dozens of places so that your long term albums don't have hundreds of internet cat meme pictures and screen shots from iOS?


I would recommend sitting down with a nice cup of tea or coffee and a large piece of paper and just list out what devices you want to take pictures from, what the master collection looks like, and how you'll manage things coming in to and out of that master collection.

Once you've done that, you can look at iCloud through a web browser - https://www.icloud.com/#photos and get a good picture of how close that "master collection" is to your ideal collection. 

Then look at your Storage Settings - https://www.icloud.com/#settings



If you are running short, pay a little $$ for one month to buy yourself time and space to get everything safely into iCloud.

Then you can decide if you have a computer to hold things and want to make use of the free iCloud photo stream to get all your photos onto that computer or if you want another solution (google has one, dropbox has one, yahoo/flickr has one, many custom services exist for amateurs and pros to store photo libraries online).

Best of luck. The site will be here for you to ask more narrow questions once you have decided how to steer your ship. It's hard for us to advise you on broad plans - but once you make the broad plans - we can help you navigate certain bends in the river or certain customs officials that are prickly to get your on your way to happy photo management.