1) you're welcome
2) VC handles buffers fine down to 64 samples, below it gets unpredictable and very dependent if you sequencer support e.g. 32 samples and of course your hardware. if <256 doesn't work for you you need to tell us more about your setup in order to help you.
3) the virus still receives CC data even in virus control mode. you can switch to Remote Control mode and select the Virus A-B-C template to try that out.
4) the delays all work. the maximum delay time is something like 623ms - if you exceed that by choosing a low tempo and a small divider the virus automatically will choose the next possible preset. if you miss a certain value, calculate it and use a manually chosen delay time.
best, marc