Ner’ro,
You are beginning to get the right ideas and a good approach. Looking at the Stabber fitting you posted, and bearing in mind I’m an Amarrian pilot, so roll with my ignorance, there are a couple of thoughts.
The rigs: I can see why you are thinking of greater warp speed (wait 'till you fly Battleships or larger!), but increasing the maximum warp speed won’t get you around most systems much faster, typically only a few seconds are spent at maximum warp speed. If you are looking at fast travel then it’s reducing align time that is important. You may be better off replacing one with an Ancillary Current Router. That will solve the power grid problem instantly.
The underlying problem could be the two large extenders and a MWD. Look at trying one extender and and some hardeners. Pick the hardeners based on the missions you are flying - or failing that EM and Thermal to fill the resistance holes. A mission appropriate hardener and a shield extender rig will roughly equal a large shield extender and save about 130 grid. Enough you can realistically put something useful in that empty mid-slot. Or upgrade the guns.
And using hardeners prevents you having a huge signature - the bigger the signature, the easier it is for big weapons to hurt you.
And while we’re there: the Autocannons. I like your using lower calibre weapons - they are often overlooked; they have very useful tracking bonuses if your skills are low, but seriously look at higher meta versions: the 220m Medium Prototype Automatic Cannons do more damage for slightly lower fitting requirements - the downside is it’ll add a million to the total ship cost.
I’m Amarrian, so I avoid Nanofibre in the lows - it reduces armour amount (most Amarrian ships are armour tanked rather than shield based) - for better damage application look at fitting Tracking Enhancers to increase fall off range (you are going to be fighting in falloff range - it’s a characteristic of Autocannons) or shield power relays to speed up shield recharging.
As I said, you may want to ignore or vary the above. There is no “right way” to fit a ship. It always depends on skills and what you are planning to do with the ship. All I hope is to give you ideas and the reasons behind them.
Remember: the limits on PG and CPU are there to force you to pick your own balance between firepower, mobility and defence within a particular hull. Your ship won’t excel at everything (it’s a Minmatar bucket of rust with a signature after all), but it will serve you well.
Terak.