When oxygen is not present, the cell cannot perform oxidative phosphorylation. Glycolysis occurs, but there will be a buildup in NADH, the electron carrier, since it cannot shuttle the electron to the electron transport chain. Animals undergo lactic acid fermentation to recycle NAD+ in order to continue glycolysis.
Lactic acid will accumulate, but since it is an acid, it will lower blood pH, not increase it.
Substrate-level phosphorylation still occurs during glycolysis.
Fatty acids will likely still be oxidized/broken down to provide additional energy because of the shortage of ATP.