Hi Dave,
Using the FMs to upload the data directly from excel files is a bad idea(will have a very bad performance).
You can first convert the excel file into CSV file or a text file and then upload it.(Here you have many options to upload)
There are no ABAP restrictions on number of records to be uploaded but there might be some system restrictions.
I would like to suggest 1 thing.
Rather than uploading 1 huge file, the same can be split into multiple files with less number of records, say 60000.