There are two limiting factors: the length of the combined URL, and the size of the combined file. The max file size is controlled via
ModPagespeedMaxCombinedJsBytes MaxBytes
and I think it's set to 90kb by default based on experimentation done a few years ago. That is, having fewer large files made our tests slower. You could try to increase it but I'm not sure it will benefit your users.
The URL length limit is based on issues we've seen in proxies, and may be a bit conservative. You can control that with:
ModPagespeedMaxSegmentLength 1500
But I'd first look at whether you need all those scripts! That's a lot of scripts there, especially considering you've already combined some of them.