Not a problem. I just bought a small 8 ch subsnake to go from my mix position (Stage Left) to the middle front of the stage; I realized at our last show I was running 8 30' cables:
4x vox
2x keyboard/guitar player
2x monitors
Now with the snake, I lay one cable, the snake head lives between the monitors and smaller/more manageable cables for the 8 needs.
Mics - I'd upgrade your mics and bass DI before effects, but that's me. Why? Too many gigs where we got there, had zero time to setup before playing, and didn't set up effects. For bar gigs, ensuring vocals are clear and feedback free should be top priority; effects would come next. In fact, running things dry gives you more time to play and mix levels vs. worrying about effects types/levels. I'd spend money accordingly there. SM58's should sound better than a PG48, but never having had a PG48, can't say.
Jeff's point is equally valid; since the OP is playing while mixing I'm, trying to recommend solutions that Keep It Simple from what I've learned.
Amp/Drum mics - I haven't heard the Nady so I can't comment on their sound quality; I have found that in most of the bar/pubs we play in, we haven't needed to mic drums other than possibly kick and snare, and then rarely. Guitars - the SM57 is a great all-around mic; there are many mics better than it for specific jobs, but you can't go wrong with a few to use on guitar amps, snares, vocals, etc. Also they're $100 and not more.
Feedback Destroyer - I had an older one (the DSP1124P) and never used it as I didn't have time to fool around with it. Friday I set one up in our rehearsal room, and it's definitely not a 100% solution - it kills a big part of the sound, and there's lots of grainy system noise in there (I knew this going in that it wouldn't be perfect, and for $75 4 years ago, it owes me nothing). Are you using this on your Kustom Monitors? I'd suggest getting either a DBX231 or similar and use this to ring out the monitors; if you then want the Feedback Destroyer on after as a safety measure, great but I wouldn't use it as your be-all end all monitor EQ. While they do have parametric EQ, cutting with sliders is a lot faster when you're under the gun. I did just get a FBQ2496 for $50 on eBay to replace the older unit, and will see if that makes our rehearsal space more livable. Better monitors down the road will help tremendously with your feedback woes as will mic placement.