Here we go, frothing again. =P
To be honest, I've never met an adult snake that wouldn't take f/t. All of my adult snakes will eat live, pre-killed, f/t. They'll eat rats of the appropriate size, mice, hamsters, gerbils. The only thing they snub their noses at are day old chicks.
Like Dean had said, if you don't want to accept the possibility that feeding live may be a necessity at some point, then maybe snakes aren't for you. And I mean that in the nicest way possible.
I've had to use live several times to get a reluctant feeder to eat. I've used live to spark the feeding in a post egg-laying female who didn't seem interested in f/t. They're a primitive brained animal and who knows when they're going to be turned onto the idea of live food. They're not that domesticated yet to accept whatever we throw at them. But for snakes, I'd say they're pretty darn good.
Feeding live pinks through fuzzies is a breeze for the most part. It's over quicker than you can shake a stick at. Feeding live adults poses potential hazards of biting to the snake, albeit in all the times I've fed live adults, I've never had it happen. But then again, I don't think accidents are on a timescale.
But luckily most snakes can be tricked into thinking its live with a pre-killed mouse and a pair of tongs. Unless you're squeamish about killing mice yourself.
But like Roy said, I wouldn't worry about feeding live right now. Take a deep breath and relax first. It isn't all that big of a deal to get worked up about.
If you need him weighed and don't have a scale, I'm sure most vet offices would oblige you for free, I know mine locally doesn't mind. Just make sure the weight is in grams, which is what most of us are used to.
Most of my healthy sized males, depending on varying lengths, are 400-600grams. And that's on an every 10-14 day feeding cycle. I would say anything above 300g would be ok, which is the minimum weight at which females need to be to safely breed. And I've had smaller males than that do the breeding.
When its breeding season, they will fast, but I've never had any visibly lose weight and look thin. Most of mine will give it up after a couple of months and go back to regular eating. Some of mine may refuse 4-5 times in a row and then eat once and refuse some more. They're all different.
I think its just common sense on how they should look. Look at your younger ones, nice and round, it should look the same proportionally on adult snakes as well. You don't want the sides sunk in or the spine showing.
Here are some pics of my adult males of varying weights:
Vlad - 605g - 2001:
Pepto - 340g - 2001:
Ungeheuer - 350g - 2002:
Granite - 330g - 2003:
Cardiń - 185g - 2003: He's a small, short guy..