Yes, you can. The boots state that you use them exactly as if you had used the spell teleportation. That means you gain all effects of the spell, exactly as if you had cast it on yourself, including the ability to take people with you.

As for how many people you can take, the spell allows for one medium creature (or lower) per three caster levels. If we check the boots we see they have a caster level of 9th, and so you can take 3 medium creatures or less with you, allowing you to take the entire party of 4 medium creatures. However, beware of encumbrance limits when hauling back treasure from a dungeon. You will probably want Heward's Handy Haversacks, Portable Holes, and similar carrying aids, to make sure you are not heavily encumbered.

If the fighter carries the warlock

He is carrying:

• 56 lb of his own gear
• 242 lb of half-orc
• 10 lb of warlock gear

Total: 308 lb versus a carrying capacity of 255 lb so he's going nowhere.

If the fighter pushes, drags or lifts the warlock

He is still carrying 56 lb of his own gear which is less than the 85 lb for being encumbered so he isn't.

He can easily push, drag or lift the warlock because 245 lb is less than 255 lb. If he pushes or drags him, his speed is unaffected because what he is pushing or dragging is less than his carrying capacity. If he lifts him, he can't move because he is now exceeding his maximum carrying capacity.

TL;DR

Whatever you are carrying goes to your encumbrance - this affects your speed. If you are carrying stuff and also someone who is carrying more stuff then you are carrying all of that.

In addition, you can push or drag up to your carrying capacity without changing your (encumbered) speed, however, if you push or drag more than this (up to twice as much) your speed drops to 5 feet.

At the absolute maximum, you can carry 15 times your strength score and push/drag twice that much again.