Review my router UPS design please.

hey.

The basic project is an UPS for my router and ONU. I think its pretty self explanatory, The Attiny will be programmed to turn off the mosfet so the boost converter cant Over-Discharge the batteries.
The voltage divider is there so my possible input range ( 12V-3V) stays within 1V to 4V for the attiny to moniter.
The relay configuration makes sure my adapter and the batteries dont meet.
The charger is a TP4302B board with a single dw01 onboard. I cant find any 1s bms with enough Amp rating so i just have to be extra careful not to draw too much juice, The router and ONU draw near 12.5 WATTS, say 15 watts. I may join some other load which will never cross a total of 30 WATTS.
This is the Buck and the Boost converter im looking to buy, both of which are (surprisingly) based on xl6009e1.
Im somewhat of a beginner so i prefer that someone with a bit more experience can check this out. ( This got me into a lot of trouble earlier, Im not a complete noob holding a soldering iron for the first time, I have just started getting into system designs and all. this is my 5th project of this catagory)

Please leave your thoughts on this, that would mean a LOT