The stem looks fine but if I were you id look in the For Sale section of this forum and pick up some other bars. Those bars you have are reeeeally flat and wide looking.
For trials, a wee bit of upsweep on the bars will feel more comfortable. Something along the lines of Trial Tech or TryAll bars... There's plenty to choose from in the FS topics just now.
Chain wise, you'll want a KMC 610 - 3"32 width (buy new! should only be 10-15 quid) and pair that with a sprung tensioner, one jockey wheel or two. Either should be fine but a double wheeled tensioner will give you more chain wrap on the rear cog. If its a single cog tensioner, you're best trying to get the chain as tight as you can, almost to the point no tensioner is required.
When comparing trials bikes and street trials bikes, generally the rule of thumb is...
Trials bike, easier to keep on back wheel for back wheel hops, like gaps. Street bike, the bars and stem are usually set higher and closer to your hips, meaning it should be easier to do things like bunny hops and pulling up to manual.