I would not use that for long term. Charging battery with high current will wear out the battery sooner. 3.5A is 1.5X 2A. 2A is max you should really use.I drove down to the thrift store and found an old Nintendo Game Cube PS. It was rated 12V 3.5A. I swapped the plugs and it works great.
These tablets come with 7200 mAh battery (or 7.2 Ah). With 2A (per hour) charger, should take little over 3.5 hours to fully charge it. ie, 7.2/2 = 3.6 hours With 3.5A takes, 2.06 hours. ie, you are fast charging with 3.5A. ie, slow charge is usually close to 4 or more hours.
Battery will last longer if you continuously, without draining, slow charge it. I would suggest not going less than 3 hours max for charging. 2.5A is probably the max I would go with for charger. That is really pushing it. 2A, 1.5A and last choice 2.5A.
With my 12V 2A charger, the battery gets fairly warmish. I can only imagine how hot your battery is getting with 3.5A.
Later,