Welcome.
Which exact capture card?
BT8x8 is/was a terrible card overall, but especially from some brands.
Location = USA, check. So NTSC, correct?
What exact audio card? Note that most Creative/SoundBlaster are pretty terrible for capturing. Fine for video games, horrible for video timing. Also very tinny in general, no depth, regardless of bits.
USB audio cards never work for capture. And that card is a Creative. No, it doesn't matter than the card is "professional", it's not professional for using in a video workflow. It may not go beyond 44.1kHz, either at all, or under certain scenarios.
All of your capture/audio card problems could be resolved with a specific USB capture card for under $150.
Why did you settle on this setup? Are you attempting to scrounge gear? If so, realize that never works well, or at all.
That also begs the question: What are you using for VCR? TBCs? Because random VCRs, no TBCs, will give random (bad) quality conversion. The incoming signal to the capture card matters, so even the best capture cards cannot be fed a bad/junk/crap signal.
Capturing shouldn't be, doesn't have to be, this hard. Proper gear is all that is required for capture/ingest to not be a PITA.