The bearing setup is wrong and will not be effective. It will be the equivalent of having one bearing. Standard bearings are not intended for axial loads. They can take a bit but you can't preload them like you need to for this application.
Though the use of a ER collet chuck is a good start.
The angular contact bearings need to be used in a minimum of a pair. They also need to be preloaded. Preload is determined on several variables including running speed and load. For something like a PCB router you can get away with a lighter preload than say a milling spindle. Heres the thing though. You can get bearing sets that come with the inner races ground to set the bearings to a specific preload. They will have a suffix of something like DUL (Duplex, Universal install, Light Preload). If you can't get the bearings you need in a preloaded set then you will have to set the preload though spacers where the spacer between the inner races on the spindle is a few tenths of a thousandth shorter than the spacer that separated the outer races. The parts can not be made on a lathe. The must be ground.
Spindle design is not easy, but there are materials out there to help. Timken/Fafnir has a section in one of their books that covers the basic designs of spindles. You can download it here: http://www.timken.com/en-us/products/Do ... -09-29.pdf
Starting on page 137 is cross sections of various basic designs. Most vertical milling machines Use a duplex of spindle bearings at the bottom and a single radial ball bearing neat the top of the spindle housing.
Good bearings are not cheap, though you can find NOS bearings on ebay for a fraction of their new cost. I had to replace the bearings in my surface grinder at about $150 a pop, times 4...
I may have a small set of preloaded AC bearings that may work for you. What is the OD of the collet chuck?
There are water cooled chinese made spindles on ebay that are pretty cheap. Look like a real good deal for the price. Though you will need a VFD to drive them.