Giving them the 2% or whatever they might need is not going to give the donor any power over anything so it would not make a difference, the DA can continue moaning about Putin while they are enjoying their ministerial perks and whatever they get out of the arrangement. It won't really be about aligning because you share similar values or anything like that, I will be a marriage of convenience that keeps the EFF out.
The problem with the EFF is that they are the biggest threat to the ANC than the DA, they will go with the DA because it is a safe bet, they might be the second biggest party but the ANC knows they are not a threat to them, they will stay a 20% party for a while. One day when Zille is confined to a retirement village maybe the DA can find its way out but for now they are the perfect partner.
The only thing that's going to be a problem for the opposition is that if they are seen to be scrambling to partner with the ANC they become dispensible, which erodes their bargaining power, but that's what they will deserve if they cannot unite.