Hello Pedro,
Welcome to the Forum!
1. There are at least 3 (ACTIVE) options that you can choose from that have Power Path option and can be used with lead acid and multichemistry batteries. They have similar features with the Bq24745 having a SMBus interface. Also, its operating temperature is from 0 to 125 whereas the other two BQ24702/3 operate within the -40 to 125 deg range. The BQ24703, will automatically switch the load to AC when the battery level drops below the battery depleted level, while the BQ24702 will not.
2. Pulling the Enable pin high will cause the PWM output to go high. This will turn off the P-MOSFET and all charging will stop. This is implied from how a P-MOSFET operates.
3. You can override the the automatic switching function using the ACSEL. If you want to stay on battery power after the AC adapter is plugged back in, then set ACSEL low. In the example circuit found in the data sheet, the ACSEL is pulled up to Vref so it would follow the process outlined in the Autonomous Selection Operation found on page 22.
This is from the information gathered from the data sheet. You can do a search on the forum to see what real world issues others have had with these devices.
Thanks,