Hi there,
1 - If by invoice you mean the email sent to the client, you can basically go to System>email and unpublish the mail sent. This require a commercial version of Hikashop though.
2 - This indeed looks like a bug. Could you look into your database, in the table xxxx_hikashop_widget. Search for the entry Last 7 orders and copy this code in the widget_params field:
O:8:"stdClass":27:{s:7:"display";s:7:"listing";s:9:"date_type";s:7:"created";s:10:"date_group";s:5:"%j %Y";s:10:"periodType";s:14:"proposedPeriod";s:14:"proposedPeriod";s:9:"thisMonth";s:6:"period";s:1:"0";s:7:"content";s:6:"orders";s:7:"filters";s:45:"a:1:{s:14:"a.order_status";a:1:{i:0;s:0:"";}}";s:15:"category_childs";s:1:"0";s:9:"customers";s:14:"best_customers";s:15:"customers_order";s:5:"sales";s:8:"partners";s:14:"last_customers";s:14:"partners_order";s:5:"sales";s:12:"compare_with";s:7:"periods";s:14:"period_compare";s:4:"none";s:5:"limit";s:1:"7";s:6:"region";s:5:"world";s:6:"format";s:5:"UTF-8";s:10:"map_source";s:8:"shipping";s:12:"product_data";s:5:"sales";s:16:"product_order_by";s:4:"best";s:15:"orders_order_by";s:4:"last";s:8:"compares";N;s:10:"categories";s:3:"all";s:8:"products";s:6:"a:0:{}";s:7:"coupons";s:6:"a:0:{}";s:6:"status";s:0:"";}