Regarding towing a boat with a Subaru Forester, here's my deal.
I have a 2011 Foz 2.5x. According to the stats I've seen, it can tow up to 2,200 or 2,400 pounds depending on where you find the stat. I have not seen anything about a split capacity base on trailer brakes for my car. At the time, I found the lower stat, and the Outback had the higher capacity, which I attributed to the Outback having a slightly longer wheelbase.
My 192 lists a displacement of 1400 pounds. And we know how reliable that is likely to be... (seriously under-estimated, for sure.) Trailer is something like 500 pounds on the title, and who knows how accurate that is? So, you can be pretty sure that when I tow, I am at my tow limit, if not over. And I mostly tow with almost nothing in the boat, and the 5hp 4 stroke in the back of the Foz. I typically tow the boat about 15-20 miles at a time, over rolling hills of Southeastern PA. So, really, not very stressful terrain at all. But I am also paranoid of destroying my transmission, and of jack-knifing while braking, so I don't generally go on highways, and even if I did I don't go over 50mph.
Your Foz is older than mine, and I know my year changed to a new engine design, so it has a bit more torque and HP than your 2006 Foz. I think you would be perfectly fine towing a Vic 18, lighter than my 192, depending on what your towing needs are. If you are like me, back and forth to my lake once a year, over slower back roads, I surely don't think you'd need trailer brakes.
Now, when I bought the Foz, I had a Boston Whaler Harpoon 4.6, which specs about 450 pounds, trailer, what, 300-400 pounds? I used to tow that up and back from the DE and NJ beaches 2.5 hour trips, and at 70mph (but not all that time. There was that one time I was trying to get somewhere before they closed. 70mph was nuts.) Then I went and bought the O'day, but didn't upgrade tow platforms. I would love to get a 6 cylinder vehicle, which would get me somewhere around 4K or 5K pounds of tow capacity (Nissan Pathfinder, 5K.) If I wanted car payment again, I'd be able to tow to the Adirondacks, or Chesapeake, or anywhere else, really, with impunity. But I also know that my fantasies of vacationing on the boat are unrealistic, and the reality of a car payment again really sucks.