Get rid of the plastic hose barbs, those white plastic fittings are probably nylon which love to crack where you cannot see the crack, go and get brass which will last you almost forever. I have had a lot of white plastic fittings break soon after putting them into service until I realized that they just don't last out in the real world and replaced all with brass or black poly but mostly brass.
Get rid of the clear polybraid, it will collapse easily, especially on warm or hot days, that is probably your problem along with the nylon fittings.
Do not buy galvanized or plain steel fittings as they will rust quickly and give chunks of rusty metal to your pump and help ruin it soon.
I would run 1" line from the tank to the filter and then "T" it to both sides of the pump if you want to but Being only 5.5gpm, I would use 1" all the way to the pump and then it reduces at the pump, been doing that for a while now and no issues.
I would also run a larger stainer/filter, open it up and take a look, a lot of times you can have trash stuck in there and not flush out, open it up and take a look in there and see if it is clean.
Being in the south like I am, open up your tank and see if you have algae growing inside it, the algae will break off and clog your screen fast and that stuff will not flush out, I like the big bowl screen filters so I can see the trash in there and know when to clean it.
Unloaders can be bad when new, if you have another try it if the other stuff does not work. My Hotsy had an AL607 unloader on it and it lasted 7 years, then now I have to change it out every year or less, they just don't make quality like they used to just like everything else. I like that unloader because it fits in the small place.
Hope this helps.
