Hi -
This is one of those things that makes the InfoPath to SharePoint thing a little ... sticky.
The short answer is - as far as a promoted property in your form library, your choices are going to be limited to functions like first, last, or merge (which is what you are currently seeing the results of).
A longer answer is - you could submit your repeating data to a seperate SharePoint list so that you have a list item for each item in your repeating table. InfoPath doesn't have built in functionality for that, but the company I work for has a tool that can help you do this - it's called qRules and here's a link to the product page.
Additionally, this can be done with custom code - so if you are a programmer or have one in your organization, you may want to consider that option.
Oh - another option for you, as I re-read your question - what about calculating your allocations in the form? Is that possible? Then you could just promote the result of the calculation?