So exactly what is the issue you are having - you list two totally different ones
1
When I import photos into my Macbook Air, I delete the photo off my iOS device, but then the photos disappear from my computer as well. How do I fix this issue?
This is not an issue and there is no fix because there is no issue - you are using iCloud Photo Library and that is exactly how it works - it is a syncing service and every change made on any device (additions, deletion or edit) is made on all devices - for devices with limited storage you use optimized photos -- you can not "fix" something that is working correctly exactly as documented
2
I'm having trouble sending photos from the icloud on my iOS device, how can I fix this?
For this we need more details - what are your iCloud setting and status on each device? The most likely cause is that everything is not yet uploaded and nothing is downloaded until the upload is complete - but until you give us details we are only guessing
LN