Good questions. Let me add a two more quotes (and by the way let's restrict quotes like these to the relevant parts to help understand the point)
Net Wrote:An entangled creature can escape with a DC 20 Escape Artist check (a full-round action). The net has 5 hit points and can be burst with a DC 25 Strength check (also a full-round action).
Compared to spider's net, where EA DC, break DC and HP are functions of spider size, this is pretty much different so I take the statement "similar to an attack with a net" in the spider's description with a grain of salt.
Entangle (spell) Wrote:... causing them to become entangled. The creature can break free and move half its normal speed by using a full-round action to make a DC 20 Strength check or a DC 20 Escape Artist check.
In my interpretation while the spell refers to the same named condition ("entangled") it imposes more severe restrictions on movement. Namely, you must spend a full round action to make the strength or EA check [b]
and move half your speed (in case of Torin, 10 feet) and the check must be repeated every round. Add to this that it has a huge area of effect and long range, all in for a first level spell.
Tossing game balance questions in the side lane for a moment, let's compare the three things.
As a side note, once again, movement specified for races (e.g. 20 for dwarves) is distance in feet, not speed in feet per unit of time.
Your default speed is the walk speed which is your movement per round. Your battle speed is the hustle speed which is your movement per move action.
So to avoid ambiguity I will use "speed" for "feet per unit of time" and "distance" for "feet". Numerical figures are given based on Torin's movement of 20.
An entangle spell is definitely an immobile barrier in space (read: all three dimensions) and thus it impedes your movement more but you cannot break free completely until you reach the edge of the area. If you are not entangled then you can move at half speed (effectively treat it as difficult terrain).
A net is thrown at you and unless tethered you can move with it... somewhat. It's harder to escape than a spider web and harder to break free than the Entangle spell but it has HP so you can cut your way out. It is definitely not "anchored to an immobile object" so you can move but then the entangling object moves with you so you remain entangled. While I haven't done historical evaluations for me it seems that you can move like on difficult terrain.
A spider's web doesn't have roots but it's sticky and clings pretty well to stone, hence the idea of sheet webbing on floors. So I would say it's pretty much "anchored to an immobile object", i.e. the floor. So I would say it's pretty much like the spell and not the weapon, except that EA DC, Str DC and HP vary and that you can actually break free.
So to summarise:
Escape / Break free - Entangle: full round temporary, Net: full round, Web: standard action
Cut through - Entangle: no, Net: yes, Web: yes
Move - Entangle: half walk speed (walk speed if saved), Net: walk speed, Web: half walk speed
Now to your questions.
Q: Can you move by half speed while you are entangled by a spider web (as a move action)?
A: You can move at half "normal" speed i.e. half distance (10') in a full round or quarter distance (5') as a move action.
Q: Can you take a 5-foot step action?
A: No, you cannot take 5-foot step on difficult terrain and as I wrote consider entangle spell (unless you saved) and spider web as
more difficult.
Q: Can you crawling/rolling 5 feet as a move action?
A: Crawling, yes, provoking AOO. Rolling, is it specified somewhere? What's the difference from crawling?
Opinions everyone?