One needs to spend 10K, not 5K, to unlock 2%:
"SAM'S CLUBŪ BUSINESS PLUS MEMBERS

Amount of Year-to-Date Purchases Percentage of Purchase
(including the current Purchase) Eligible for Rebate
Up to $1,500 0.25%
$1,500.01 - $3,000 0.50%
$3,000.01 - $5,000 1.00%
$5,000.01 - $10,000 1.75%
$10,000.01 - $1,000,000 2.00%"

"However, Year-to-Date Purchases over $1,000,000 will not be eligible for a rebate."

The maximum rebate is not 20K, but slightly less:
$3500*.005+$2000*.01+$5000*.0175+$990000*.02=17.5+ 20+87.5+19800=
$19925

And, with anything less than well over $10000 you are actually losing money due to less cash back as compared with fidelity 1.5% cash back, gas/drug/supermarket 5% cash back, etc AND $99 fee.

So go with the Fidelity 1.5% cash back, no annual fee.