Somewhere, you have a leak that's allowing your fuel system to bleed back down and losing its prime and causing hard starting.
If I were you, I'd clean every location where you removed a hose, screw, fitting, housing, anything in the fuel system when you changed your filter, and clean those areas CLEAN and make sure they're DRY DRY DRY.
Then get your vehicle started and let it run a minute or so and running smooth and then shut it off.
Then go to the fuel tank and remove the cap, and stick and air nozzle into the filler neck, and shove some rags around it to try and seal it up to some degree so you're getting 5 to 7 psi of air pressure pushing into the fuel tank. I'd even regulate my air down to around 20 or 30 psi coming out of the air compressor, just to be sure you don't overdo it.
Then after a minute or two of pressurizing your fuel tank and fuel system, go back to every location you cleaned and see if you see any diesel leaking at those locations. I bet you'll find your leak location pretty quickly.
AZ is right, don't use starting fluid in your engine if at all possible. In your situation you need to, but don't keep doing it. What starting fluid does, is washes your cylinder walls clean of oil, and when your engine cranks and goes on the compression stroke, that pressure forces the piston rings against the cylinder wall and without oil it will gouge the living hell out of both rings and wall. VERY quickly, you won't be able to start your engine without the starting fluid. Diesels can get addict to SF very very quickly.
If you do need to use SF in cold weather starts, do it like this......
1. Remove your air filter and set it to the side
2. Spray SF into the air filter housing, a 2 or 3 second shot for starters and see how long it burns
3. Light it on fire, and keep your face away from it
4. Go crank your engine while you have a good fire going
That fire preheats the air going into your engine and makes for very easy starting without damaging your engine with SF. You may have to do it a couple times depending on how cold it is. Don't worry if it's plastic because that plastic can handle HIGH engine temps, and besides, that plastic is as cold as the temp outside, and you have cold air passing through that plastic when cranking and the engine when it's running, so it will never melt. I mean you can hold your hand on the plastic and see it's nowhere near hot, let alone melting. Just don't sit there soaking it with can after can of SF, use a little common sense here. Besides, by the time you ever get that plastic to its melting point, you'll have had your engine running already.
Also, NEVER spray SF into the housing while cranking the engine. You do not want to risk getting that in the combustion chamber as raw fluid as it will wash the cylinders clean of oil.
Also, you don't want to risk raw fluid hitting a glow plug, because that can destroy your engine. It can break connecting rods, knock a hole in a piston, and even stretch head bolts and lift the heads from the block.
Starting fluid is a great tool, when used properly.
This is basically how old diesels were started in cold weather. They had a steel pipe that was part of the air filter housing that was between the air filter and the engine head, and threaded into that steel housing, was a glow plug. Next to that glow plug was a nozzle and hooked to that nozzle was a tube coming from a small hand pump on the dashboard. You would push a button and get that glow plug red hot, and pump that small handle for the hand pump, and that would suck diesel from the fuel line and spray the fuel across that glow plug and it would start a fire in your air filter housing and preheated your air going into the engine for easier cold weather starts. Now they just moved the glow plugs inside the engine in each cylinder, but they did start using them in the air filter housing before redesigning the engines.
Using SF in this manner is just going back to old school ways of doing things.
It worked great, but you had to have a working knowledge of glow plugs and not overheat and pop them, but this was back when Men had a working knowledge of things they owned, and nothing was automated.