Temp/Fuel Gauge remains flat. Van will not start. All other electical works

First of all you must never remove the battery cable in a misguided attempt to reset something. Besides introducing a new and common problem, you have a miserable HVAC computer that that loses its memory and will have to be reprogrammed to stop the yellow leds in the push buttons from blinking. Half of the procedure can be very frustrating and to work, the air conditioning system has to be working.

The Engine Computer lost its memory when the battery was disconnected. Fuel trim data will start to be rebuilt as soon as you start driving it again, without you noticing, but it will have to relearn "minimum throttle" before it will know when it has to be in control of idle speed. Until then it will be hard to start, and may not start unless you hold the gas pedal down 1/4", it won't give you the normal "idle flare-up" to 1500 rpm at start up, and it will tend to stall at stop signs. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

Please clarify ". And she cranks but when they remain flat the van tries to start for the briefest moment. But doe not crank".

Do you mean the starter stops cranking the engine? If so, and it does crank after repeated attempts, that is due to worn copper contacts in the starter solenoid. Most people just replace the entire starter, but those contacts can be replaced separately and very inexpensively. Many hardware stores and farm and home supply stores have the kits.

For the two gauges, a common cause of intermittent anything on the instrument cluster is loose connector pins. They can be soldered to the copper circuits to make a better connection.