Your regression analysis is suffering from 'data overload/clutter'.
First: You want to make sure your data samples were collected from a normalized distribution (meaning, you want each independent variable's data samples to be greater than 25 items. Anything less starts introducing data biasness and will form inaccurate conclusions). So get rid of the independent variables that you do not have 25 or more data samples from. And if you must use non-normal distributions you should use the Box-Cox procedure to convert and "normalize" them.
Second: You want to use data where there's some paired observations. That will help reduce 'accidental correlations'. For example, a fast food restaurant may notice that high customer satisfaction surveys seem to indicate preference for lower prices and bigger portion sizes. So you would have to collect surveys that have high customer satisfaction and see what the portion size was and what the price was that day and use those data sets. We are not using random variables like population density with no observable correlation.
Next, I would run each independent variable separately as a simple linear regression. The Rsquare is showing you the strength of that correlation, BUT YOU MUST VERIFY that this is not a chance variation. To do this, take a look at the calculation's P Value and compare it to the significant value you chose (usually .05, although you mentioned you are using .10). If the P Value is LESS than the significant value then the results are SIGNIFICANT, meaning not a chance variation. But that's not all, you also need to check the significance of the coefficient of the independent variable. Do this by finding the calculated 2-TAIL P VALUE next to your independent variable. If that 2-tail p value is LESS than your significant value, then the coefficient IS SIGNIFICANT. You should be able to see this visually as a scatter plot as well.
Once you do this for each independent variable you will be able to weed out the insignificant ones this way. Then run a multiple regression test for the strongest independent variables. Remember to check your 2-tail p values for each of the coefficients (independent variables). If they are less than the significance level then THEY ARE SIGNIFICANT and the correlation to the dependent variable is not by chance, it is true. It is not unusual to have some coefficients calculate to be significant, and others not. Remember this is showing CORRELATION not CAUSALITY.
Really the goal is to verify or analyze those independent variables with the strongest correlation to the dependent variable so you can get a working equation to predict how changes (increases or decreases) in these independent variables might affect the dependent variable. I would try to narrow it down to 3 independent variables.
When you run the multiple regression for 3 variables you'll see it gives you an estimated Regression equation.
Sales (Y) = -2.95 + 0.0149(portionsize) + .5572(price)
Simply multiply in values for the (portionsize) and (price) to see how they affect sales.
For your research, you need to reduce your data down to the important variables that are statistically significant; which independent variables do I want to know (realistically) if I could increase, or decrease, how will this impact my dependent variable.