Not sure where you got your information from!
Firstly, so what if they were male? Yes, boar taint exists, but, in traditional breeds, I've never had a problem with boars sent off up to about 8 months old and I always choose boars over gilts for pork because they tend to grow better. My own go for pork at five to six months (normally six) and I've had no problems with taint and lots of repeat customers - both buyers of meat and buyers of boar weaners.
re. feeding, do you mean 6lb a day each? If so, yes, that's too much. Mine would be on 3.5lb to 4lb max (depending on time of year/how cold it is, etc).
Killing weight? Mine go at about 90kg, which gives a dead weight of about 60kg. You can buy a special tape measure called a weigh band/weight band which goes around the body behind the front legs and over the shoulders and gives you an approximate dead weight, although you will need to deduct a couple of kilos because Tamworths tend not to have ample back ends. There is also a calculation which I have somewhere on my other computer - you measure with a normal tape then do a calculation to work out the weight. I'm sure someone will post it soon - or Google it.
Good luck and feel free to message me if you have any queries I can help with.
Liz