I would appreciate any feedback on the attached PCB. It is my first moderately complex 4-layer, working with a size constraint of 30mm X 70mm. It is a data-logger with GPS, IMU, Light sensor, and Temperature sensor attached to a SAML21 running at 12MHZ and logging to an SD card or SPI flash chips. This is a prototype so there are large test points on the bottom and two different memory interfaces (deciding between SD card or daughter board with SPI NAND). 
there is not much silkscreen due to size constraints so I colored the nets. Bright red VCC (3V3) while pink is the USB-VBUS and rusty red is the positive battery terminal. Dark blue is GND. Light green traces are I2C buses running at 400KHz, light blue is SPI buses at 1MHz.
The main questions I have are:

· 
The two power circuits at the bottom of the board. The left one is a Lipo charge IC (MCP73831T) and the right one is a buck-boost voltage regulator (TPS63051RMWR). I tried to follow the suggested layout as closely as possible. Since this is a 4-layer board I have solid VCC and GND planes on the two internal layers. Should I expand the pours around these power circuits? are there enough vias connecting the existing pours to the inner layers?

· 
Should I have more pours in general on the outer layers? I was avoiding external pours to avoid more vias stitching it all together, and possibility of loops. I ran into my fab house drill limit on a previous board and I wanted to avoid that.

· 
The IMU, light, and temperature ICs are QFN parts, with a fairly small pitch (especially the IMU). I had issues soldering on previous boards with these chips, and so I removed the solder mask from the traces just outside the chips, with the idea that is would make rework easier since I could get an iron and some flux in the reflow a stubborn pad.

Generally anything else I may have messed up and am unaware of? I attached my “top” schematic sheet that contains all the power stuff, and a printout of TOP and BOTTOM with colors as described before.

thanks!