Can a human get sucked into a jet engine?
Yes. Human beings can get sucked into jet engines if they are close enough- this has happened multiple times in a number of aircraft ranging from A319 to A6E intruder.

However, it happens only in rare cases- usually in case of miscommunication or a mistake, when safety procedures are not followed. The following image shows the safety hazard area for aircraft engines.



A warning poster, available from Boeing, reminds ramp and maintenance workers
about the dangers of engine ingestion; image from Boeing Aero

In addition, the engines also have hazard-area warning decals on the nacelles to warn the ground personnel of the dangers.



Warning signs on engines; image from Boeing Aero.

As for the maximum weight that can be ingested, it will vary with the engines, though they have been known to ingest items from safety pylons to baggage containers, and of course people.