Missions & Complexes

Based on what you post here your character is not ready for level 4 security missions unless you have a vet to go with you.
Level 3's may be difficult as well depending on the rest of your skills, guns are only a small portion of a good mission ship / pilot combination.
Do you have any tanking skills trained?
Do you have any capacitor skills trained?

Essentially to help we need to know more about you and what ships you like / think you would like to fly.

Blitz or not that is the question.
See the end of this post for a good link for mission runners.

First to blitz a mission means to kill only the few select ships or structures you need to, collect whatever you have tyo collect and then get out. Blitzing can be very cost effective but you need to know every mission and what you need to do to complete them and be effective. Also since you are not killing everything in the mission as you progress through it can place even greater stress on your tank as you will have many ships shooting at you and for a longer period of time.

A modified way of blitzing missions is to kill everything but do not loot or salvage the wrecks.

Kill it all then loot and salvage. This is usually best done if you have 2 accounts or friends to go with you. One kills while the other follows along behind and loots / salvages. However there are many who run missions solo and bookmark a wreck in every pocket(room) of the mission, turn in, change ships and then go back to loot / salvage.

Which of these basics methods is best is a decision that only you can make.
I can give you many posts worth of reasons why each of these is best, or worst.

Now that link
http://eve-survival.org/wikka.php?wakka=missionreports

Looks to me as though you have spread your SP too thin and in one main area, gunnery. It's a classic mistake.
And one I narrowly avoided after taking my first battleship in to a LvL3 mission and getting my arse handed back to me.... ON FIRE

First off you need to pick a 'goal' ship, a ship you want to use for LvL4's, for me this was the Maelstrom.
So the steps I took where: Thrasher (destroyer) to> Cyclone (battlecruiser) to>Maelstrom (Battleship).
So imho you need to focus on single race's ships in the beginning, and each ship I used had the same basic setup: Active Shields, Projectile Ammo and a low rack full of damage mods.

But.... you NEED core skill before you need T2 guns (T2 guns was the last thing I trained)
Without core skills in defence (armour/shields), engineering, fitting, rigging etc.. your battleship is gonna get carved open in L4's the first time you try, so there is little point training all gunnery if you cant stay on grid for more that a minute or two.

Do not underestimate the role drones have to play either, once Elite frigites get under your guns drones are the only thing you'll have to kill them. The last thing you'll need in squishy Battleship is the be webbed and scrammed with drones that to no damage and a ton of incoming DPS. It will end badly.

For missions, if you have the option of 4s, you should do 4s IMO. If highsec mission running is going to be something you do on regular / semi regular basis for isk, 4s are going to be where you get your money, so you best get familiar with them now.

Your damage is going to be low. Blitz missions because the less time you spend in combat the better your isk/hour is going to be. On missions you cant blitz, it may be worth going back in looting/salvaging in a noctis if you have the sp, just because you're going to be gaining alot of isk per time looting compared to the speed you'll be collecting bounties. I also want to make the suggestion of doing missions for minmatar. Guristas have long range rats + jamming, and you wont deal kinetic damage very well. You wont get guristas missions in min

The trick to clearing 4s with a low sp toon is range. When you pull range, the incoming dps, your cap usage, and enemy angular, will all be very low. That being said, you should make sure you you have the skills for a micro jump drive. If you have one equipped and off cooldown, it will pretty much guarantee you dont lose your ship to mission rats. If you get warp disrupted and rats start breaking your tank, jump. If frigates get under your guns, jump. etc....

Maelstrom is really going to be your best option right now. Typhoon isnt going to be all that great with your missile skills and the tempest kinda sucks at life in general. Pushing battleship up to 4 would be a good idea because the maelstrom gets hull bonuses for dmg and tank. You also want to make sure your range and cap skills are up to at least 4 if you can.

Here would be what I would suggest, keep in mind I havent had to do a low SP setup for PvE in a long time, so you may need to tinker with it a bit in EFT if you lack fitting or have alot of fitting left over. Any t2 modules you cant use, just sub for t1. Make sure you can use t2 gyros though, they're good and dont take long to train. Also, use mission specific hardeners:

[Maelstrom, Very Newb Fit]
Gyrostabilizer II
Gyrostabilizer II
Gyrostabilizer II
Tracking Enhancer II
Tracking Enhancer II

Tracking Computer II, Optimal Range Script
Large Micro Jump Drive
X-Large Shield Booster II
Explosive Deflection Field II
Kinetic Deflection Field II
F-90 Positional Sensor Subroutines, Targeting Range Script

1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L
1200mm Heavy 'Scout' Artillery I, Fusion L

Large Projectile Ambit Extension I
Large Projectile Ambit Extension I
Large Projectile Burst Aerator I

This is all good information so far but it should come with a caution.

With 5 mil SP and nearly half of that in small guns and another 700k in armor and shield hardener skills it is not likely that the OP is ready for level 4's.
Do you have all your rigging skills trained? Without rigs to support them those tech 2 mods just add to the cost of a ship you will have to replace when the rats hand it back to you in pieces.

Do you have your CPU skills up?
How abut electronic and targeting skills?
And since a low SP lvl 4 ships ill most likely be a battle ship how about your large gun skills?

I am not, and never will tell you that you should not do something in this game you want to do. What I am saying is that based on 5 years of working with new players in missions and accounting for the scatter shot nature of your training to this point I am strongly advising you to stay out of level 4 missions for now. Level 2 and level 3 should be what you are looking for.