Toilets, Sinks, Showers, Tubs and Disposals - Toilet not flussing and gurgeling

Ok here is the problem. About 2 months ago the toilet started to not flush properly all of the time. So I would plung it and it would be fine for a couple of days then it would happen again so I would plunge again and it would work ok agian. Well now when you flush the bowl fills with water and slowly empties out but if there is paper in there it wont take paper until it really breaks down. And when I take a shower or flush the toilet upstairs the toilet with the issue gurgles and burps.

So yesterday I took the toilet off and cleaned it out and ran a fish tape down the drain and diddnt seem to hit any clogs. I also dumped 2 5 gallon buckets of water down the drain and it took all 10 gallons with out any problem. So I reinstalled the toilet and flushed it with no luck I have the same issue still. I was told this might be a vent issue and try to run the garend hose down the top of the vent pipe on the roof and so I did. I took the traps off of the bathroom sink and kitchen sink assuming that the toilet was vented with one of those and I could hear water running in the bathroom drain but seemd to gurgle in the kitchen drain.
So before I go and try and get into my attick and start looking for the vent I want to know if this sounds like my problem or am I barking up the wrong tree. Any help or suggestions would be greatly appreciated.
Thanks for your time in advance.

Sounds exactly like a vent problem. You may try power flushing the vent out from the roof with a high pressure garden hose other wise it will take a long auger (snake) to thoroughly get the vent unclogged.