Just changed head on '98 volvo 940.Coolant keeps

Did you bleed the cooling system after you reinstalled? Chances are high that there are trapped air pockets in the system. Those systems will thump you big time for not bleeding them (sometimes repeatedly) after a water pump change. It's possible, though unlikely, that the head gasket failed. Start by bleeding the system until it is free from air bubbles (heater in car set to max!) and that should take care of it. As for the oil leak, that could be due to the overheating condition you experienced.

a secondhand one is possible and do it yourself if you really want to keep the car ,but you have to come to the point where is an old car like this thats only worth 500euros max worth all that work or do you move on and buy a newer vehicle

What color is the exhaust? If it is white with a sweet smell to it you are burning antifreeze. In which case you would have to se where you went wrong with the cylinder head replacement.

Everyone always jumps to head gaskets. There are plenty of MINOR things that can be looked at first.
The Volvo 2.3, 2.4, 2.5 Inline 5 Cylinder dipstick tube is known to develop a large amount of condensationin winter months and stop and go driving. What you see on your dip stick is possibly just condensation. Take off your oil cap and look under the cap and inside the valve cover. Is there any thick foamy oatmeal like substance or noticeable amounts of water? If your oil was saturated with coolant, you would be able to see it up there too. Check your coolant for oil. Volvo coolant is typically brown to orange, however make sure there is no sludge. Start the car with the cap off and keep an eye out for alot of bubbles. A large amount of bubbles is a sign of a bad head gasket. A couple here and there is just air in your cooling system.
Coolant, Transmission fluid, and Oil have several places they can mix. If you have a turbocharged Volvo, the seals in the turbo can go bad and cause a mix of oil and coolant. Your transmission cooler is also in your radiator, and if it cracks your transmission fluid and coolant can mix. I believe turbo models have an oil cooler built into the radiator as well.
Overall if your car sounds fine, you dont see oatmeal, your not using coolant and oil in excessive amounts, dont have white smoke, and your turbo isnt whining you probably just have condensation in your dip stick. If you are overly concerned you can send a sample of your oil to a lab and have it tested for traces of coolant. Headgaskets rarely fail on Volvo's, even the old ones....I have seen many that have gone to replace them have not found a failed gasket and end up finding a bad transmission cooler or a bad turbo.

I am a volvo tech and your problem is fuel pressure ralated and i had same problem in 1995 850 turbo and the fuel pump was the problem and a used one is around 35.00

You could try some block sealer but the only real and best way is to change the gasket.

Check the turbo waste-gate actuator spring for proper tension.

yes it has a crank sensor below the dist in the top of the trans bell housing

Probably IS the crank position sensor-classic symptoms. It is hard to reach (of course)-behind head at top of transmission bellhousing.Not a very expensive part-try it.Will the car fire at all? If so,then it may be the IAC-try holding down the gas pedal slightly if it runs,replace this.

Have you checked compression on non firing cylinders? Likely has blown head gasket between these two cylinders if located side by side.