I believe our app Better Reports may be able to help. We can show Total Sales split by all the payment gateways used for an order, total number of transactions for that order, and filter specifically for those orders with split payments. These reports can be exported directly to Excel, csv or pdf.
In addition to building custom reports to meet your specific needs, you'll have access to 60+ built-in reports that cover many common use cases for merchants and our reports can be scheduled to send to your email or Google Drive at set frequencies.
I encourage you to install Better Reports and start your free 14-day trial, and I'll be happy to set this up for you.
Let me know how you go and feel free to reach out if you have any further questions.