Before I waste money on plumbing parts I don't need...

I have a 29G tank and a Rena XP3 filter. I want the Rena to work thru the bottom of the tank -- I'm going to try drilling my own holes, so wish me luck on that one. I plan on putting the holes 2" from the sides -- one on left rear of tank and one on right rear. I'll have the intake with basket just above the substrate. I'll probably have the return as gray pvc (with Loc-line) with 2 spray nozzles: one just below the surface and one about half-way up the pvc.

I have a couple of questions:

1) These XP3 hoses are a weird size: 5/8" ID (17mm or so). Should I go with 3/4" bulkheads in the bottom of the tank for intake and return? And, if so, do you think that I'll be able to jam these hoses onto a 3/4" barb? I know to heat up the hose. (Jamming those hoses onto the fittings that Rena provided was not easy.) Maybe there is some sort of adaptor I don't know about.

2) With the filter coming in thru the bottom, my glass lid is going to fit very tight and will not have any air holes (unless I put some in). Will there be any issues with the fish getting enough O2 or the plants getting enough CO2 (though this is a non-CO2 tank)? My lids in the past always had holes for pipes, hoses and the like.

If you see any flaws with my above plan, please let me know. Or, if you have other ideas I might want to consider, I am happy to hear them.