Not boost the current, boost the voltage.
The job of the charger is to transfer the maximum
power! Not current or voltage.
1>There needs to be a way of keeping the battery from overcharging.
2>You need to look for the 'sweet spot' in the PV VI curve, and try to keep the panel there. How to do that?
The LTC3780, or some PWM, needs to not regulate current or voltage but regulate power. The PIC's job is to keep the panel at its sweet spot.
Start
Get some power from the panel
measure power I*V=P (usually input but output should work)
delay 100mS
Start of loop
Increase the current a little, (OR decrease a little)
delay 100mS
measure the power.
If the power increases you are going the right direction (up OR down)
If the power decreases you are going the wrong direction, reverse (up/down)
go to loop