Venue requires urgent help!

[Phillz600]

Ok so we are having quite a few problems and need some help.
I am not tech savvy first off, I hired someone to put in a PA system with our own speakers and have had nothing but trouble since he put the system in.

Basically when I was hired a few weeks ago as Venue Manager, I came in and saw that the system the venue had been using was just an utter mess, small 8 channel desk with 2x 1000watt speakers, was never used for much but acoustics.
The new owner that hired me saw the same but not wanting to put much money into it he bought some new speakers and we have lent a desk from another computer which came with an impressive rack (ha).

What we hired in:

Behringer Eurodesk MX 2442 - 24 channel 4 bus mixing console.
Behringer Multigate Pro - Quad Expander XR 4400
Behringer Crossover Pro - Dynamics Processor MDX 2200
Behringer Autocom Pro Dynamics Processor MDX 1400
Behringer Ultra Pro Equaliser
'The Sssnake' 16 channel send Stage Box

What we purchased ourselves:

2 x SRM 1850 Powered Subwoofers (1600watts each)
2 x SRM 650 2 way Powered Loud Speakers (1600watts each)

What we already had which we are using:

2x Laney CXP-110 Monitors (130watts each)

The problem we are having is that the EQ isnt really working, vocal channels keep cutting out and sometimes we have to change the channels just to save time as things happen during performances. And we are having a major problem with feedback, so much of a problem that its effecting the venue's image of live music.

Is this something that could be wrong with the equipment or shall we replace the desk and rack?
Also another thing you may need to note is that the venue is very small, could it be that the speakers and equipment is just too good for the venue? Our venue is 100 capacity, I know of venues in London that have bigger systems than ours and similar capacity but do not struggle with these things.

Got a big american band coming in next week and hoping theres some ideas that could help get through the night lol.