the bulb will glow and ammeter will show the reading
The Positive side of the Ammeter should be connected to the positive side of the battery and the Negative side should be connected to the Globe/Conductor/Insulator to provide a valid reading.
i=v/r can be used to it
You'll get a reading on the ammeter showing 15 mA
The current decreases due to I=V/R. The ammeter reading will decrease as R is increased.
In series
Smoke. Since a voltmeter is in parallel with the load it is right across the source voltage. Putting the amp meter across the line with its low resistance it will act like a fuse, hence the smoke. Newer solid state testers are usually smarter that the operators. They have built in circuitry which sense the wrong settings you are using and shut the tester off with a "beep" to let you know that you are doing something wrong.
decrease to half of its original value
That would have to be a 'wattmeter', but they're seldom available. In terms of more readily available instruments, you'd need to use a voltmeter, reading the battery's voltage, and an ammeter inserted in series in one of the battery's connections, reading the current from the battery. The rate at which the battery is supplying energy at any moment is then the product of the two meter readings.
The Thevenin equivalent circuit of this battery is 1.5V and 0.6 ohms in series. A more exact answer cannot be given without knowing the actual resistance of the 2 meters (I assumed infinite for the voltmeter and zero for the ammeter, as would be for ideal meters).However I would NEVER attempt this test as you describe it, many types of batteries will explode like bombs when shorted (as they would be when an ammeter was placed across them)! The correct way to do this test safely is with just a voltmeter and an adjustable high wattage resistor.
The positive terminal of the battery would be connected to the positive terminal of the ammeter. The load would then be connected between the two negative terminals, positive side of the load being connected to the negative side of the ammeter.
If the charger has a ammeter on it then it should show close to zero which means the battery is no longer pulling any current from the charger which would mean the battery is fully charged. If it has only a voltmeter then it should show 12.5-13.5 vdc