Mathew To answer your last question first what I think you're referring to is actually the Hillsboro Canal which runs through the everglades areas from Lake O and along the southern border of the Loxahatchee NWR.You are not allowed to trepass on the parts through the agricultural areas though you can hike but not bike on the part in the NWR but that won't do you any good.Also from Canal Point,Pahokee,Belle Glade or South Bay you can take Palm Trans bus #40 into WPB for $1.20 and then connect to trirail to Broward so that may be an option for you with a easterly route.
But after reading your original routing which I hadn't before my last post I kind of like it and here are my thoughts on it.When I rode to Wauchulla(from the east) I took 66 west from 27 and then cut north on Clifton Bryan Rd. because the shoulder on 66 stopped at that point.I then worked my way north to 64 on very scenic uncrowderd backroads .On 64 at the v intersection where main st splits off to Wauchulla that you are routed out of there was no shoulder so I continued on 64 which did have a shoulder to Zolpho Springs then up to Wauchula on 17.So if in Wauchulla you don't like the looks of main st headed east you might detour to Zolpho and pick up 64 there.Probably all the roads between 64 and 66 are going to be fine and I like your routing avoiding 27 as much as possible at the start of day2.721 south from Brighton I am not familiar with though I have thought it would make a good route sometime if it has a good shoulder and or low traffic.You could remain flexible and check it out and if it doesn't look good then continue east on 70 to Okeechobee as in the alternate routing.
The thing I like about the 721 routing assuming it is a suitable road is that it allows you to still go east or west on the levee or on roads.Assuming you take 721 alot depends on whether your bike is suitable for dirt levee with a few small rocks here and there.Assuming it is you can take the more direct shorter western route either on the dirt levee or 78 to south of Lakeport.South of Lakeport the levee ends for 2-3 miles while crossing the Fisheating creek watershed so you have to take 78 there.At the southend of the watershed is where 78 becomes dangerous but where the dirt levee begins again that you can take on to Moore Haven where again it is then paved to South Bay.A nice thing about the levee is there are free primitive COE camping sites every 10 miles or so and one is located west of Moore Haven where the levee makes a sharp bend from southerly to easterly so that would make a good day2 camp assuming you are camping.
If you don't want to take the bike on dirt from the intersection of 721 and 78 I would take 78 north to Buckhead Ridge where the Kissimmee R. flows into Lake O and at that point the levee is paved all the way to Port Mayaka.Get on 441 a short ways to Canal Point(from Port M. where you have to get on 441 anyway to cross a bridge around a water control structure) and once again the levee is paved all the way on to South Bay.Keep in mind on the levee there are various points you will have to get off and onto the roadway to get around water control structures etc.Here is some info on the levee.
http://www.dep.state.fl.us/gwt/guide..._scenictra.htm
Your alternate route on 70 has good shoulders all the way through Okechobee and then 441 south to the lake has a wide outside lane though congested.Looks like you are trying to route on back streets through the town though.27 south from South Bay is high speed like an interstate though so if you don't like trucks barrelling by the bus to WPB then trirail to Broward may be an option.If you can't tell I have biked around Lake O twice (once this past weekend)and backpacked around it last year and plan to do that again soon as well.Have fun.