Looking for some input on a bow build

So I'm working on a Bow build for my Ranger and I have some questions regarding my options/ideas.

First thing, I am planning on keeping this pure Dex if that's feasible (if not, I'd appreciate an explanation for why it won't work out). Given that, and that this is a Bow build, much of the rest is up for debate though. Currently looking at running Split Arrow for AoE (it plays really nicely with Fork from past experience), not sure what to do with my other 6L I will have eventually (a better single-target skill for faster boss kills seems like a good idea, but I'm not sure what to run, Ensnaring Arrow looks interesting, but doesn't play well with Pierce, so if I go that route, I will be specifically avoiding Pierce).

1) How much increased maximum Life should I get out of the skill tree? I plan on probably running high Eva+Dodge and Wind Dancer (note the 20% less Damage taken if you haven't been hit recently), so I figure all my life pool really needs to do for me is be enough that don't get 1-shot by anything I don't managed to avoid. I know most people recommend +160% max Life or more for endgame, but I feel like this setup could skimp a bit? I can only find about +100% max Life within the Ranger's area, so I expect I'll to have to path into one of the other character's areas or both neighbors to get the rest.

2) Besides life, I'm curious about debuff options. It seems Blind and Poison are the only debuffs that have pure Dex support (Maim and Bleeding are attractive to a Phys bow build, but not readily available). I am also considering if I should invest into crit or not, the issue is that I won't be running the Int support gems for crit, so I'm not so sure it'd be worth it (this may also depend on if I go with poison or not), are there enough skill points to spec into crit and poison and make both worthwhile?

3) Anything not mentioned you think I should know/think about regarding this type of build?

Not sure what do you mean by "pure Dex" here. In general, there is ZERO reason to invest extra points or gears with Dex, since Dex only gives us a little accuracy and a bit evasion. It's totally not worth it, unless you want to do a cold Dex stacking bow build (which is very expensive and not beginner friendly). If you are refering to Dex based skill/support gems, again there is ZERO reason to use pure Dex gems. You should use any gem that are best for your build, and it can be any colors. It is relatively easy to fill the attribute requirements for the gems you need in general.

Seems to me that you are not sure about what kind of bow build you would like at all. Probably you should check the build guide list, pick one that you like, and just follow the guide:
https://www.pathofexile.com/forum/view-thread/1810170

In general you need to choose among these categories: chaos damage over time build (Toxic rain/Caustic Arrow, most beginner friendly), poison bow build, bleed bow build, elemental bow build (usually Barrage + ice shot/tornado shot/lightning arrow). The passives and gears would be completely different depending on what type of build you choose.