Virtuemart: Quite a few problems

Hello,
I have used the gk_quark_ecommerce_quickstart_J!3.zip pack to build a small e-shop. All seemed to work fine, until I've reached the end of the project, trying to configure the payment systems, the tax amounts and such. Various, nasty problem surfaced:

1 - Clicking the VAT item in the Taxes and calculation rules (or trying to create a new one) results in : An error has occurred. Table calc_categories not supported. File not found.

2 - Whatever payment system I configure, clicking on the CONFIRM ORDER button in the front-end results in: AN 0 ERROR OCCURED DURING YOUR REQUEST

3 - Moreover, I had to disable the whole error report div in the frontend via CSS for presentation purposes, because whatever value I set as a safe path (including the one suggested by the system, and even if I give the safe path folder 777 permissions) the system throws an error.

I'm not new to Virtuemart and I know it's actually a very bad choice compared with other e-cart platforms, but this is too much. I don't know if the problem is with the template or with the jumpstart installation, but this is really leading me to question my lifetime subscription to this site. The templates look great, but if they don't work properly and are going to backfire like this, aesthetics is useless. Sorry about my tone... I'm really stressing out about this.

Hello,

For me all described issues are strictly connected with the virtuemart code (especially the 2. point which is an issue caused by changes in Joomla! 3.5.1 API). Please contact VM support regarding it.