1) The problem with using an ISM band for earth to space is precisely because it's exceptionally noisy. You want the best possible SNR for two way satellite, either direction. With a small satellite that orbits relatively close (LEO to low MEO, compared to geostationary), which will likely have a system architecture composed of numerous focused spot beams... If you were to design a series of spot beam on the satellite body with ISM band antennas aimed at major cities all you would achieve is gathering noise.

2) Not going to help much unless the upstream is so little that's basically useless. The same antenna is used for both Rx and Tx so you still need significant gain to overcome the path loss and have sufficient link budget for the space-to-earth traffic.