Existing abs 1 1/2 in. Must remove and slope opposite way to new dry well must I relocate autovent?

By "auto vent" do you mean AAV( air admittance vent)? Where was the old auto vent installed? I hope you plan on installing a grease trap,(see image) before the dry well. If you don't grease and fiber will clog the dry well leach holes in time, And bye the way. If you haven't built the dry well yet here's a dandy way to do it,(see image) Good luck, Tom

Thanks Tom great advice! Yes it is an aav the existing aav is located close to shower p trap. I will be reversing(slope) opposite way. Should I keep aav close to p trap or locate it to middle of my pipe run? I also thought of adding a couple of clean outs just in case... what do you think?

I see! The AAV is venting the shower and not the dry well drain. Leave the AAV just behind the showers trap. What else will you be discharging into that dry well? Back to you, Tom

All together there would be 1 shower, 1 small bathroom sink and kitchen sink with dishwasher. It is a small cootage so not too too much use.

Does the kitchen have a garbage disposal? With all the grease that you'll be sending out to the dry well a grease trap will save you from having to move the dry well because of clogged leach holes. That way you can simply clean out the grease trap instead of moving the dry well. Good luck, Tom

No garbage disposal. I will be installing grease trap. Do it once do it right! Right!