Not a bad start, but being a more or less fresh level 40 you're at the weakest point in your entire leveling career. So don't worry if you feel weak. At this point in the game most people feel weak, even weaker than when they were leveling and being bolstered.
If you have the gold (if you don't, get a crafting skill), try to squeeze as much stats out as possible. Get decent talismans, at least 20+, but if you can afford it, 23+ on all your gear from now and +24 on stuff you know you're going to be wearing for a while. Also buy potions. +80 int / +660 armor until you're intelligence capped. After that, switch over to +5% spell crit liniment/+60 wounds liniment. Healing potions are also very, very good for BW since you'll constantly be damaging yourself. Get the restoration potions that heal over time, and if you have spare crests buy some instant healing potions too. Crafted potions and potions bought with crests are on seperate cooldowns.
I would also add that in RoR it is very common to mix sets in order to make use of the 2-piece and 3-piece stat bonuses granted by most sets. This can help beef up your statline at low RR.
Yep. This is normal. It will get much better once you start gearing up. However, you'll also need to practice the fundamental skill of positioning and kiting. You need to develop a feel for whenever you're putting yourself in the enemy's crosshairs. Remember everybody is out looking for squishy targets like you! A rough rule of thumb if you're running solo or pug warbands - never be the guy on the frontline. Once you perfect your positioning skills your true enemies will become apparent: Witch Elves and your own greediness.
Further, here's an option to consider;
While BW is inherently a squishy class, you do have options to make yourself a lot more tanky, and I believe that is not a bad option for inexperienced players at low rr. You could opt for a more defensive approach (sets like Beastlord and Vale-walker allow for this), slotting +wounds talismans and when your healthpool is high enough even toughness/armor talismans. Your renown points you could spend in Futile Strikes (reducing your chance to be crit), which is probably the single-most important stat when it comes to survivability. You also have a tactic that allows you to heal yourself.
The obvious trade-off is that your damage will be lower, though personally I've played with these types of builds extensively - pretty much while leveling my Sorc from 1 to full Sov I played defensively and I liked it a lot. I've also done a lot of solo roaming with defensive DoT spec builds. (you can find videos if you search for 'Solo Sorc PvP' on youtube for reference).
I've found these builds very useful if you often find yourself in situations where you cannot rely on support.
500-800 crits are probably a result of your damage being mitigated, by guard, resistances, absorb shields, etc. This is also normal, and you have tools to deal with this and otherwise your team mates will have tools to deal with this. Make sure that you're at full combustion if you really need to kill something fast.
As for disruptions - again this is normal. You are not yet intelligence capped and in addition to increasing your damage it also reduces the chance your spells are disrupted. The soft cap is at 1050 and you should aim for this. That will reduce the disruption-issue somewhat.
However, you will likely need more. Armor sets also provide disrupt strikethrough. I think the Beastlord set provides +5% strikethrough - very useful at low rr. In BiS gear I run about +8% strikethrough, in addition to being intelligence-capped, and I'm actually looking at ways to get more. It's an important stat.
For duels, yes. Kiting is paramount and DoT specs help you deal damage on the move.
For scenarios it's different since you will have teammates to function as bullet spunges. Though DoT specs can still be viable since they help with mobility, making positioning easier. Your burst damage will be lower, but your sustained damage higher. Especially at higher skill levels burst tends to be favored, but going for a sustained damage build can be very good while learning the ropes.
Positioning really is the key. If you want to go for a more stationary hard-nuking build/rotation your positioning has to be crisp.
It only gets better from where you are now. If you enjoy the class, don't let this demotivate you. When you start upgrading your gear and tweaking your build/rotations, you'll be killing players literally in one second. (the so-called 'timestamp') and you'll also be a powerhouse when it comes to AoE damage.
In all fairness, Sorc/BW aren't the stars at the highest levels of play and they could use a tweak here and there, but they're certainly viable. I main a rr88 Sorc and it's my favorite toon by a mile.