your cpu is the problem
csgo is source engine based and the source engine is a cpu engine
and your i3 ist really underpowered when it comes to streaming doing one thing at the time its okay but if you try to game on an i3 you literally cant stream with x264 yet you could try using qsv to get rid of the streaming load on the cpu and let the integrated gpu on that cpu do the encoding but since you are running an sandybridge(2nd gen) i3 i doubt that your motherboard supports qsv since the qsv hype really started with ivybridge(3rd gen)
still here are some suggested settings for that cpu
preset ultrafast
resolution downscale by 1.25 or even 1.5
fps between 25 and 30
cfr=unchecked
scene buffering time 700
everything else can be stay as it is