1 def/pray capability questions

Hey guys Mindtain here, this is my first post so I'll give you a brief introduction to my RS history...

I started playing the same year they stopped the rare holiday drops..(my luck haha) and have made countless accounts in my time, my main was hacked/stolen and perma-banned in 08 (8 years to go...if the timer even goes down) my pure is still alive and has 200 days till 10 year Cape..

Anyway I've always been fond of range pures and the restrictions they offer so after about 5-6 years of not playing, my roommates influenced my to make a new account on OSRS (I hate RS3)

Here is my account so far, I've decided to try out a 1 defence and prayer build and train range through slayer with minimal hp gain from the other cmb skills

I will be 89 range when I get to 72 slayer (my only goal so far)

82 range

70 hp

30 att/str (from waterfall)

57 combat

1 def/pray

And currently 63 slayer

My main questions are:

1. How possible is it to kill Wyverns with no prayer

And if so what ranged item is most efficient

2. Is it possible to get a fire cape with no prayer

3. Approximately how long will it take to reach 99 fishing through barbarian fishing (with and without 3 tick method)

4. Have they nerfed the tzhaar city drop rate? I was there for over 160k exp and no obby drops

(Just today was the update for ring of wealth so maybe it's changed)

I have some more questions but i will ask at a later date, thank you for your time