They do make this model with a membrane fabric for waterproofing: https://www.campsaver.com/oboz-sawtooth-low-bdry-hiking-shoe-mens-vfewo.html
Silcone may not hurt them, but will not make this shoe waterproof. We would recommend using something less industrial such as shoe waterproofing by Nikwax. Let us know if you have any additional questions.
To obtain the best fit I typically encourage customers to get a style that is made in a wide width unless you can try each boot on with the socks you would wear locally. You can sort through our footwear section by checking the Hiking/Backpacking box on the left side of the footwear web page. Then check the box on the left for Wide Width and this will show you the boots that we currently have in stock. For what we have in stock right now in wide widths I would recommend the Asolo Fugitive GTX and Vasque's Breeze 2.0 GTX or the St Elias GTX for hiking.
If you will be doing some backpacking as well I would recommend the Vasque Bitterroot GTX and Summit GTX, Asolo Power Matic 200, and Lowa Renegade GTX.
These are all high quality styles that perform very well and some of which I have used myself. I'm not sure the type of terrain you will most often encounter and also which traits you prefer (ie. weight, durability, breathability etc) but hopefully this has helped. Feel free to contact us with any further questions!