How to obtain average and total impact factor of publications for an academic?
I'm not aware of any specific tools like ResearchGate which provide an average impact factor for a researcher - maybe others know of something? However, you could fairly painlessly generate the average SJR/SNIP value for a researcher through SciVal in Scopus. 

If you add a researcher in SciVal, then click on the benchmarking tab, and then click on View list of Scopus Sources for the selected Researchers and Groups this will bring up a list of journals the researcher has published in. You can then click on Export and download the list of journals, with their SJR/SNIP values into excel, where you can then just use the =AVERAGE formula to calculate the average. I just did this and it took me 3-4 mins max. 

Back to your specific question, you could use InCites to follow a similar process as above to calculate a researchers average Journal Impact Factor (Thompson Reuters) however it's not as straightforward as SciVal. As far as I know, you can't generate an XLS list of journals a researcher has published in within InCites (so you would need to get this list somewhere else). You can however export a list of journals from InCites with their impact factors but you would then need to link your researchers list of journals with the incites list to collate the relevant impact factors. you could use excel VLOOKUP to do this and then calculate the average. This is a lot more effort though, so it would depend why you want this average measure of research impact in the first place and whether it might be enough to just use the scopus impact metrics.