I believe you are good to go.
1. If it says it is automatic, it likely is.
2. It should automatically kick itself down as it approaches 100% charge. But start on 10amps when charging.
3. I don't know. The instructions make no reference to gel batteries.
4. Only you can decide that.
Some of my thoughts.
I don't like the analog dials, but prefer an actual readout of what the charger and battery are doing.
I also like a fully automatic charger ( although some folks probably like to be able to tinker.)
I have a B&D smart charger and it has a button for flooded(wet), AGM, and Gell batteries. It has a digital readout and can begin with a 40 amp charge to get you recharged faster. It progressively lowers the amps automatically as battery is charged and displays the amps digitally to the nearest 1/10.
The digital readout also displays FULL when battery is 100% charged, and it has a series of error codes (with code explanations listed on the back of the machine) to tell you if something is wrong (dead battery, incorrect connection, etc)
It seems pricey on Amazon at $150. The link at cars-update has it for $99, but I got one on sale at Menards for around $70. I've had it for a couple years and it continues to work well.
Link here