You already have the kick up board so you just need kick up rudders now. These should do the trick.
http://www.ebay.com.au/itm/Mirror-GP14- ... 27cd064cf1
I use one on my dinghy and they work great. I believe some here may have set their boats up with them (Dave maybe?) They will work fine if you run over sand bars, just dont back into a sand bar like I did

Luckily, around here, we are "mostly" dealing with sand and mud so hitting the bottem isnt generally that big a deal (unless you do it at speed in an M in which case you will snap the daggerboard).
What size fuel tanks have you got? If the common 45 litre ones, you will be fine. I only have the two 22 litre ones and then a spare 20 litre container. I havn't actually been to Amity but we may try and get there over the holidays. From what I'v heard its pretty hazardous trying to get from there to Moreton (???) Fuel is a problem on the bay. Theres Manly of course. we almost ran out once near Macleay Island and basically just made it to Redland bay where I went ashore in the dinghy and met a nice elderly gentleman in his front yard, who turned out to be an ex (1950s era) Sydney to Hobart sailor and he got his old car out the garadge and drove me to get fuel somewhere
Now I realise all woman are difference of course, but I still reckon you are doing VERY well to sail the boat back from Slipping Sands! I'm not even sure my wife would know the jib from the main, much less how to raise them or how they work. (to be fair, as she tells me, she is the one who has to deal with two young children while I'm sailing and doesnt have time to learn all that...)
I had the same thing happen with my motor. I heard the relay packing it in is one of the most common reasons but the other is what happened to me. The bottom of the tilt trim motor rusts (sometimes you cant even really notice it) allowing water in which kills the motor. Take a look at the tilt trim motor (especially where the wires go into it) and look for any corrosion. The Mechanic at Horizon Shores told me its very common.
We have been out through the seaway a coupla times, but it has ended up being much rougher than I expected. Last New year, we got into the bar and found ourselfs in easy three, possibly 4 metres, not breaking, but very close together - what a ride. With my young children and wife aboard, I was quite worried about the turning around to get back in once we got through the bar, but the Mac handled it much better than I expected. Having the abilities of a powerboat gives you the edge over other trailer sailers trying to cross bars. Other than that we havn't been out there, but that is only because we dont get down there enough. There are plenty of days whey you could go out for a few hours no problems at all. You can call the Seaway Tower to get an idea of conditions on the seaway. I have never crossed the Pin in any boat and wouldnt do it unless with someone who was very experienced with it, and I'm still not sure I'd do it in my Mac.
How much did that anchor winch setup cost you? Did you install yourselfs?