not sure if its worth mentioning but i just remembered how there are like VCR adapters where you can put a smaller tape inside of it to use a VCR. by no means the most ideal capture method not to mention how hard it might be finding one lol.
i did hear back from my friend and i sent him everything from your threads and he has no experience working with an external capture card similar to what you have. he highly suggested if you can find one, used or cheap new, or get your hands on an internal card that goes in your computer in the slots similar to a sound card except its for video. Primarily, the issue he mentioned concerns the software that comes with all of these external capture cards. A lot of them work and do what they are supposed to from a hardware standpoint. The issue is how they handle and capture the video in the software apparently. A lot of the more affordable video software seems to not handle video files very well and when you start working with old tape and potentially spotty time code and glitches from cheaper older cameras that record in less efficient codecs you quickly will start hitting issues where the software struggles with the incoming footage. Despite capturing via RCA cables, some other problems that you encounter can come from minimizing the software while it is recording. i know from personal experience when capturing tape via FCP that if i minimized it would stop the process which means you do need to keep the capture active. Ideally, you would want to capture directly into your editing platform for the best workflow. When you start adding 3rd party software that doesnt directly communicate with your editing platform you can risk having issues later on with goofy versions or formats that seem ok until you try to open the files, usually not a common problem but is possible. if you havent already tried, see if you can bypass the software that came with the capture card and try and capture using your editing software. The other issue that can be a problem is if the camera itself is worn out or if the tape heads are dirty which can cause issues with the computer recognizing a constant steady signal. my friend isnt really able to make much suggestions on affordable internal cards but the thing is you pretty much bypass extra software and gain a direct capture ability. you would need to check with your editing software to check compatibility for capturing the footage
the highest suggested alternative to a professional tape deck would be similar to this. blackmagic is a great brand that many use http://www.bhphotovideo.com/c/product/598248-REG/Blackmagic_Design_BDLKSDI_DeckLink_SDI_PCI_Express.html
also i recent used this exact capture card while working in Alabama last week and it works excellently and is a solid brand as well http://www.bhphotovideo.com/c/product/625264-REG/Elgato_Systems_10020840_Video_Capture_USB_Analog.html