Code for lowest power, 1 adc reading in 1 sec

I have a battery powered application. Task is to take 1 adc reading in 1 sec & then do few calculations i.e toggle two pins according to adc reading. Circuit should consume lowest power possible. Circuit has one LDO(Iq=500nA) & MSP430 only.
Is below code sequence/settings are best for lowest power:
1. Disable dc generator, disable smclk, internal 12Mhz is used for mclk. Input pull-down all unused pins.
2. Sleep for 1 sec.
3. take adc reading & do some calculations
4. go to step 2.

1. Is it correct approach or should I use 1Mhz clock for this.
2. What is best optimization setting for lowest power, currently I am using Project->Properties->Build->msp430 compiler-> OPtimization:
Opt level- 4 whole program optimization, speed vs size-> 5 speed , Inline hardware multiply->none

Current Code is below

#pragma vector=TIMER0_A0_VECTOR
__interrupt void Timer_A (void)
{
	TA0CTL = MC_0;  /* stop timer */
	__bic_SR_register_on_exit(LPM3_bits);
	_NOP();
}


#pragma vector=ADC10_VECTOR
__interrupt void ADC10_ISR (void)
{
	__bic_SR_register_on_exit(LPM3_bits);
	_NOP();
}

void adc_read(void)
{
/* enable global int bit */
   	__bis_SR_register(GIE);

/* set adc */
   	ADC10CTL0 = SREF_0 | ADC10SHT_1 | ADC10SR | ADC10IE;
   	ADC10CTL1 = INCH_2 | SHS_0 | ADC10DIV_0 | ADC10SSEL_1 | CONSEQ_0;
   	ADC10AE0 |= REG8_BIT_2;
    
	while(1)
	{
	/* 1 sec delay */
		TA0CTL |= TACLR;          /* reset timer */
		TA0CCTL0 = CCIE;          /* interupt enabled */
		TA0CCR0 = 12000U - 1U;    /* 1sec with 12Khz clock */
		TA0CTL = TASSEL0 | MC_1;  /* start timer */
		__bis_SR_register(LPM3_bits);
		_NOP();

	/* take adc read */
		ADC10CTL0 |= ADC10ON;                        //turn on ADC
		_NOP();                                      //settling time 30us for reference buffer

		ADC10CTL0 &= ~ENC;

		cnt = 1000U;
		while( (ADC10CTL1 & ADC10BUSY) && (--cnt));               // Wait if ADC10 core is active
		ADC10CTL0 |= ENC + ADC10SC;                  // Sampling and conversion start

		__bis_SR_register(LPM3);
		_NOP();

		ADC10CTL0 &= ~(ENC);                         //turn off adc module
		ADC10CTL0 &= ~(ADC10ON);

		value = ADC10MEM;
        
        do_some_calculations(value);
        
    }
}

void clock init(void)
{
    /*
     * Basic Clock System Control 2
     *
     * SELM_3 -- LFXTCLK
     * DIVM_0 -- Divide by 1
     * SELS -- XT2CLK when XT2 oscillator present. LFXT1CLK or VLOCLK when XT2 oscillator not present
     * DIVS_0 -- Divide by 1
     * ~DCOR -- DCO uses internal resistor
     *
     * Note: ~DCOR indicates that DCOR has value zero
     */
    BCSCTL2 = SELM_3 | DIVM_0 | SELS | DIVS_0;

    if (CALBC1_1MHZ != 0xFF) {
        /* Follow recommended flow. First, clear all DCOx and MODx bits. Then
         * apply new RSELx values. Finally, apply new DCOx and MODx bit values.
         */
        DCOCTL = 0x00;
        BCSCTL1 = CALBC1_1MHZ;      /* Set DCO to 1MHz */
        DCOCTL = CALDCO_1MHZ;
    }

    /*
     * Basic Clock System Control 1
     *
     * XT2OFF -- Disable XT2CLK
     * ~XTS -- Low Frequency
     * DIVA_0 -- Divide by 1
     *
     * Note: ~XTS indicates that XTS has value zero
     */
    BCSCTL1 |= XT2OFF | DIVA_0;

    /*
     * Basic Clock System Control 3
     *
     * XT2S_0 -- 0.4 - 1 MHz
     * LFXT1S_2 -- If XTS = 0, XT1 = VLOCLK ; If XTS = 1, XT1 = 3 - 16-MHz crystal or resonator
     * XCAP_1 -- ~6 pF
     */
    BCSCTL3 = XT2S_0 | LFXT1S_2 | XCAP_1;


    do
    {
        // Clear OSC fault flag
        IFG1 &= ~OFIFG;

        // 50us delay
        __delay_cycles(1);
    } while (IFG1 & OFIFG);

/* disable smclk & disable dc generator */
  	__bis_SR_register(SCG1 + SCG0);
}