I strongly recommend a full 3" fixed blade such as the Tom Brown you've already selected.
Length is important because it dictates distance. Use everything you're allowed to use.
Full tang fixed blade is important because it reduces A) deployment time, B) fine motor skills necessary to the use of folders, and C) likelihood of lock failure under stress.
Grip is vital because your life depends on it. Your Tom Brown selection appears to have excellent grip. Other knives that I can highly recommend from personal experience include the Ka-Bar TDI fixed blade (2.4 inch length) and the SOG Trident Mini, which at 3.15" may not be optional for you but remains an excellent knife. Both have extreme grip, good blades and fall within your price range.
I strongly recommend martial training in the use of knives as well. There are many excellent arts, but after 9 years of studying blade defense I believe Silat knife techniques to be the most reality-based and practical. After mastering the Silat system, you will be competent, confident and far more capable (forgive me if you're already done so - just making suggestions).
James LaFond's THE LOGIC OF STEEL is IMO the best real-life look at the nastiness of defending yourself with a knife. It is ugly - VERY ugly - but needs to be read by anyone who plans on defending themselves with a blade.
Hope that's helpful.
I appreciate this info. I'll check out the book and other info on the Silat techniques. I'm open to any other training information that you have, especially videos and self study.