My Car (opel Astra) Only Starts When I Use Starter Fluid.?

Hello!

Been having a bad week to be honest. I own a 2006 OPEL (or Vauxhall) Astra 5 door hatch (1.6 petrol engine)..Last week i ran into a problem after getting my car back from regular maintenance. I drove it home and parked, then when i had to leave i went and the car just wouldn't start. When i turn the key the engine just keeps trying to crank up. I tried jump-starting since it was a manual and it worked the first time. second time it would not (had to call a tow truck).

My mechanic has been trying to figure out the problem for the past 3 days to no avail (switching to another one tomorrow).

Anyway. what i have noticed is as follows.
1: If i spray starter fluid on the engine cap the car starts every time
2: If the gas tank is at 1/4 or less the car will either lose power and then gain it back on normal uphills or turn off completely on a very steep uphill. I just fill up some gas and it runs like a beauty without any problem.
3: After using starter fluid the car works normally, and if i try to turn it on it also works just fine. But if i park it and leave it for a couple of hours it won't start unless i use starter Fluid.

I am leaning towards the problem being with the fuel pump , Any ideas anyone? has anyone experienced a similar problem?

Just so i don't waste anyones time.
Battery is pristine, as are the coils and all the electric works. Starter is also in good condition. My mechanic told me that the gas pressure is in the green (but after this event i don't really trust his opinion anymore).

Thanks for the help in advance. Hope someone knows what the issue is

either crap in the fuel tank requires cleaning or your low pressure fuel pump is on the way out
,if you took your car to the mechanic for a service and it came back this way ,get your money back and a new mechanic

BTW DON'T use Starter Fluid Or any other ethanol type sprays there shite and will dry out your bores witch can screw up the engine completely