You may actually have the proper water/air ratio on the top port alone not needing the side ports. Unsure, as when I read first time I thought you meant the top hole was the one under water. That being said you may be on the right track. The sump gurgle you speak of may simply be the air degassing under water line causing bubbles. Can try troubleshooting by lowering sump level (if pump allows) to see if it resolves the issue. If so, simply cut plumbing above water line or drill port holes below water line to allow the air to escape. (I personally run my lines to sump above water line, had the bubbling issue when was below)