OK spent a bit more time.
Massive overdraw / bad culling / meta/ non- t-junctions* all over the map is the cause of the framerates.
Fortunately, because of the nature of your map I do think hint brushes will work wonders on most of the framerate problem areas (certainly all the indoors ones).
The beach Iām not so sure on, but I think it should be feasible with some clever hinting.
Some of the objectives in the limbo screen donāt get marked correctly.
Some of the geometry is a bit āthickā (I particularly noticed this on the scaffolding planks).
Most of the stairs are 45 degrees, and a bit big for my liking.
The tank goes through the ground lots in places (eg as it goes off the stairs into the central courtyard). Iāve got my own tank problems like that so I sympathise.
More setstate errors throughout the map.
I really dislike the autosprite lamp halos you have. They are too strong, and when coupled with the fact that the lamps donāt actually emit any light, makes the overall effect just strange. Iād say make the halos more subtle, and actually put light entities in the lamps 
What else?
Oh yeah - whatās the point of the initial satchel objective right before the tank wall???
Iām also not keen on there only being 1 route from initial Axis spawn - I was hoping you could go up the hills to the right of the entrance to maybe get on the roof but no such luck.
BUT!
The skylighting is lush, the custom textures rock (did you make them yourself?), and I think the map has a feel all of itās own.
Iām sorry the compliment bit is only a couple of lines vs the much longer ābugs / issuesā bit, but thereās only so many ways you can say ālooking damn goodā!.
Also, bear in mind I only went through finding these things because Iād love for them to be fixed because itās a map Iād personally love to play on. In other words, the more I like a map, the more critical I get 
*BTW what I mean about the meta T thingy is that q3map2, in an effort to avoid sparklies, creates extra vertices where brush vertices lie on the edges of other brushes. While this is generally cool, it does mean it can quickly create lots of extra polygons and vertices that in some circumstances just arenāt needed. I recall someone (digibob?) pointed out that sometimes itās not desirable, and gave the crenelated wall around the fort on oasis as an example of where it wasnāt desirable, and how theyād avoided it. Go to spectator and fly up to the fort roof. If you look, you can see the ābumpsā are actually set a little bit back from the edge - by doing so q3map2 doesnāt split, keeping things simpler 
Also just realised me saying overdraw was potentially technically misleading - I donāt mean it in āco-planar facesā means, just that because the VIS is so bad in places, you can be staring at a brick wall and /r_showtris 2 shows half the map behind it.