Q: Engine trouble

First thing to do is to get the oil level back up to where it’s supposed to be, and keep track of how much it takes to do so. If you have to add more than half the oil change amount to get it back to the correct level, you have probably done damage to the rod bearing and crankshaft bearings, and it’s possible the piston rings have had a minor "seizing" event in the cylinders. That would account for higher load then usual on the starter, as well as all the rattling coming out of the engine.

The clicking sound on "start" now is the starter solenoid - either from a weak battery, weak current to the starter, or burned solenoid contacts.

To avoid any unnecessary repairs, I would recommend having a certified technician, such as one from Your mechanic, perform both an inspection of your starting issue and engine noise to diagnoses these problems, get an accurate assessment of damage and cost estimate for repairs. YourMechanic.com can dispatch a mobile, professional mechanic to your location for this repair.