However, I seem to be surrounded by low-reputation people and companies that just want to take 10% (+nickels, +dimes).

I also need a carpet supplier/installer.

HML have a reputation for being flaky as hell, so qualify that referral request with "and did you personally actually close with them?"

We rely on reputation and published materials. 

Attend a meeting or two in Jacksonville to see who the reputable hard money lenders are there, you'll hear the same names over and over.  10k isn't quite enough unless you have a money partner willing to split profits on the back end. 

But how do you balance submitting low-ball offers that will make a property a good deal and maintaining a good reputation around the area without becoming "that guy"?? 

A reputation and experience are going to be important when and if the next crisis comes.  

You can pay for the material directly --pay the supplier for the material, then subtract it from the contract as you go through that part of the build. 

Are there any reputable “discount brokers” that I can look into online?

I’m most interested in buy and hold rentals....maybe turnkey if the company is reputable.