This is great. The side bar looks very professional.
The checkboxes may be a bit too large (in relation to the text next to them), but this are details.
I am not sure about adding too many custom widgets. The check boxes may have an advantage because most native checkboxes are rather small, but I think for text fields and dropdown menus it's nice to have the native look.
I am not sure and you seem to know about design, so maybe the custom widgets would fit the design.
The details can be tweaked later and I will test it on my own. I just wanted the screenshots for a first impression.