I think you did great. Any time you work with layers you are going to have a mega huge file. Merging the layers helps. Another is to save as a .jpg file type.
You did the right thing to downsize your files, which isn't always as easy as one would think because many free photo software programs don't have that capability. What they do have is to decrease the resolution, just as you did. Some do this better than others. A lot of times you will notice that the downsampled file doesn't have the details or tonal gradation that you worked so hard to get in your photo. But such is life. It will be close enough for web viewing. People have gotten use to seeing photos on their computer and forgot what great photographs really look like. At any rate, your photos won't look any worse than anyone else's.
Nerd alert: only read beyond this point if you care about how image files work:
Digital file sizes are measured in pixels-per-inch. They are given in the length of pixels per side and this will vary per camera model. For instance: the native file size for my camera is 6016 x4000. (you can do a quick google search for your camera's specs, or look in your camera's menus) This is a 24 mega pixel image. In other words, RIDICULOUSLY HUGE.
For a good photo quality print, a rough rule of thumb is you want 300 pixels per inch. If you divide the length of each side of that file: 6016 pixels / 300 pixels per inch = 20 inches on the long side, and 4000 / 300 = 13 inches on the short side. Therefore I can make a 13x19 inch print without any loss in image quality. This is the "native" size of my file. However, that's a physical print on paper. Your monitor doesn't need anything even close to that. Again, a typical computer monitor can probably only show about 100 pixels per inch. To show that file at full size on a your monitor, it would be the size of your living room wall.
On web forums such as this one, the web server is going to resize the image file anyway. You can upload a 24 megabyte file and it's still going to display exactly like a 5 megabyte file. So, rather than eat up BossDog's server storage, you can do him a big favor and downsize your file to something on the order of 600 to 800 pixels on the long side, or shoot for something around 5 megabytes if you only see a file size option.