Multiple issues after opening pool. Advise appreciated

Good Day! Recently opened my 25x50 in ground and have a couple of issues.
1. Have less vacuum pressure or flow from skimmers than main drain as noticed in the pump. The water volume drops in the pump immediately when I switch the multiport
from skimmers to main. Unsure if it's a leak or blockage.
2. Dedicated vacuum line appears to have air pockets. Without the hose the water pressure is ok. When I connect a hose(which is new, the vacuum pressure decreases.
3. When I first start the pool there is a lot of air in the lines and the water level in the pump is low.
4. I get a much better flow when I switch to recirculate than on filter. I cleaned out the filter with a hose to make sure grids are clean.
Sorry for all the questions. I've never had these problems before. Was looking into pressure testing the system for a leak or is it possible their is a problem with the Hayward DE filter. Any help would be appreciated. Thanks