Resemble lizards is easy. They could evolve from lizards, no problem. Might be more issues with having them evolve from amphibians (I think they would have to basically become lizards on the way) so let's take lizards as a starting point. They might start by finding an advantage in hunting during forest fires---the fires scare up prey, which the lizard can then eat. In order to avoid burns they would have to keep moving (like hares jumping over field burnings). One can imagine a lizard getting enough advantage from the easy prey that it would adapt to spend more time in and around fires, and thus develop thicker skin, or skin that doesn't burn easily. I see two approaches for "rarely breathes". First, it could act like a mudskipper, and basically carry a store of air with it into the fire, the come back out when the store runs out. The other option is to make it really good at pulling oxygen from the air---in order for the fire to burn there has to be a certain oxygen content (around 16%, I think), and it could adapt to breathe in the low-oxygen environment. Toxicity is a bit tougher. (Why would it need to be poisonous or venomous if there's no competition? Not a lot of things hang out mid-fire, and I imagine that that lack of competition is part of what drove it there in the first place). Perhaps a common food is toxic, and it just excretes those toxins through its skin (like the pitohui bird). As for heat-resistant blood, if the blood had a really high specific heat it could help the salamander regulate temperature, as it would take the blood a long time to warm up. Not sure how that would work chemically, but it could plausibly evolve. No digestive system---if you want it to be a vertebrate, tough luck. If you want to copy the six legs of the mythical salamander, I guess maybe it's a really weird insect? Feeds on fire---similar problem. The energy needs to be in a useful form to the body, and fire just isn't, really. Super-basic-how-animals-get-energy is they eat stuff, which they then turn into fuel to burn later when they need energy. Turning the fire into fuel is not going to work super well, because it's already undergoing combustion. Wool/cocoons. These could be the same thing---maybe it produces a cocoon, made out of "wool", for it to hibernate between fires? When the fire returns, it burns the cocoon and wakes up the salamander, which then hunts until the fire's mostly out, then it cocoons again. I think this would work, but I'm only a dilettante in biology so I might have made errors somewhere.