By the look of this, do you think I should be confident that this piece can handle the weight?
Without on-site testing, it might be a challenge to make a guess.
How do you feel about the floor being able to manage the weight?
Measure the width and length to get square meters or square feet and determine pounds per square foot or kilos per square meter. You could then test the weakest segment of the table, the ends/leafs with an appropriate lower weight that matches your calculations.
For example, I'll guess at 18" x 48", or 1.5' x 4' or 6 square feet. 850 pounds divided by six is 141 and two thirds pounds per square foot.
I'm more than 141 pounds by an unfortunate amount and I would feel reasonably comfortable standing on the open-air segment of the table. My feet would cover slightly less than one square foot which means the numbers get higher than your test value.