USPS shipping questions

I would like to be able to ship packets of brewing yeast 4.25 fl. oz. (Homebrew) in a small USPS Small Flat Rate Box. USPS website shows the cost is $4.85 anywhere in the USA.

I want the price to be the same for all areas.

I also have larger items that I want to ship regular UPS Ground using the regular shipping cost calculator. ( Cost depending on weight, size and distance, etc.)

I have USPS and UPS setup in the "Shipping Module", Zones, and have made adjustments to the settings. Priority Mail 2-3 day should be the same cost everywhere....but it is not.

Also, I do not want to double the shipping fee if the customer orders 2 or 3 units

Estimate Shipping Costs for zip code 33122
Total Items: 1 Weight: 0.5lbs Amount: $6.99

Available Shipping Methods Rates
United Parcel Service (3 Day Select) $19.31
United Parcel Service (Ground) $11.20
United States Postal Service (Priority Mail (2 - 3 days)) $5.55
United States Postal Service (Parcel Post (4 - 7 days)) $4.90

This is cost for the same item but different zip code.

Total Items: 1 Weight: 0.5lbs Amount: $6.99
Estimate Shipping Costs for zip code 97123

Available Shipping Methods Rates
United Parcel Service (3 Day Select) $11.07
United Parcel Service (Ground) $9.76
United States Postal Service (Priority Mail (2 - 3 days)) $4.90
United States Postal Service (Parcel Post (4 - 7 days)) $4.90