Now, let's understand something. While a spider with a 6-ft leg-spread (say it's about 3-4 ft across while alive given a spider's stance and gait) might not at first appear to be a considerable threat, aside from the horror factor, it is still going to one of the most vicious, deadly, and dangerous predators in existence.
First, they have excellent eyesight, easily as good as a human's probably as good as a hawk's. And it's designed to lock in a portion of the spider's brain that connects to it's fast-twitch muscles so that the spider is instantly ready to leap on its prey the instant it's in range.
Second, while it takes a lot of energy to produce chitin and the chitin on a spider of the size we're talking about is probably going to be much thinner than a normal-sized spider, remember that a single layer of chitin is stronger than steel and possibly as strong as carbon nano fibers which are 8-12 times or more stronger than steel. Chitin is laid down like plywood, in oppositional layers that provide bonding strength to one another. A single layer of plywood or chitin might not be so strong, but multiple layers of the stuff laid down in such a fashion are incredibly strong. A spider of the size we're talking about would be vicious and heavily armored.
Third, spiders don't bleed like humans do. Their internal blood has better wound-sealing capability than mammalian blood does, capable of sealing a bullet hole in seconds. The internal systems of a spider are like balloons suspended in a high pressure vat of blood that is full of puncture sealant. There is a drawback to this, of course - any sufficiently large hole in the abdomen, thorax, or head is going to cause the spider to bleed out in seconds. However, losing a leg, two legs, even three is not going to do more than cause them mobility problems due to the fact that the circulatory system is pinched in the thoracic regions leading to the legs and therefor the bleeding region can much more easily be sealed off.
Third, spiders, all of them, are armed with poisonous venom. The venom is not designed to kill, it is designed to incapacitate. Through the same set of fangs the spider then injects enzymes that dissolve the internal tissues of its victim which it then sucks back up through those fangs. The spider continues to inject those enzymes while it feeds. This often gives a spider's bite the appearance of being chewed as the spider manipulates its helplessly paralyzed, and still living, victim while it feeds. Spider venoms come in two primary types - neurotoxicity and cyanotoxic, meaning it attacks either the victim's nervous system or the blood. There's almost always a neurotoxicity effect contained in cyanotoxic venom. Very little work has been done on the chemistry of spider venom (even less on caterpillar venom) compared to snake venoms. Most spiders pack an incredible venom yield per bite by weight. The basic idea is, if a 3-ft spider bites you, you're probably dead within 5 minutes and there's not a damned thing that could be done about it.
Fourth, spiders are perhaps nature's most efficient and deadly killers. If wasps can be described as nature's psychopaths, spiders are nature's psychopathic sociopaths. They are absolutely without fear, remorse, guilt, grief, or apprehension. They'll kill each other and their own young and mates given the chance. To them you're just food.
Fifth, spiders are nature's most natural ambush predator. They can literally wait motionless for hours before striking. They have natural camouflage, sometimes adaptive, that allows them to blend in with their backgrounds and, if you can walk by a mountain lion without ever knowing it was there, a mountain lion could walk by a spider without ever knowing it was there. To makes matters worse, they can spin natural webs and nets to capture prey. Spider silk is at least 8 times stronger than steel and the glue attached to those webs has the same strength and bonding capacity as superglue. Good luck getting out of that mess before the owner arrives for dinner.
Just a few thoughts for ya'll as you start getting ready for bed tonight.
Sleep well.