Hi,
good advice from DaddyMac as as always.
Although I have no experience with a Crate amp, I performed many times with a Roland ac60 in fairly large venues i.e. Seating maybe 50 plus people, it was also fine for small patio gigs. I positioned it on a pole directly behind me ( it has a pole socket ) or in a smaller venue on a table at my side. Therefore your more powerful amp should be fine.
Now when I play venues that don't have there own PA systems, or sometimes even if they do, I use a single Yamaha Dbr10 powered speaker on a pole behind and slightly to the side, depending an how much room I have as I am frequently crammed into a corner. If feedback is an issue, tone fair it seldom is, I find that by moving the speaker directly behind my head to stop it as my body shields the mike and guitar.
I now play sat on a bar stool but still aim to have the speaker just higher than the crowd. This stops the people nearest being blasted out and the sound reaches far further.
I would imagine your amp will have a spread of about 90 degrees there for ideally you will be in the corner of the room so everyone can hear.
I use a TC Helicon playacoustic pedal for both guitar and vocal effects and also for looping. I also use a TCHelicon mo75 mike which I have found bulletproof and gives a warm clear sound.
My Hurcules boom stand sits on my right if room permits and this also holds my tablet holder.
Speaking of which it's been quite a while since I have seen a performer using a ring binder on a music stand, a cheap second hand iPad and Onsong app will allow you to sort your songs in anyway you can imagine, deal with any backing tracks/break music and be far less noticeable and less to carry. ( I will post a couple of picks of my set up and you will se how unnoticeable it is.) (I use a hybrid PRS usually so hat is what the Atomicfirebox pedal is for)
Hope sope of this helps
Cheers Steve