I have no experience with C1101, but a few things to try. First your network is not w.x.y.129/28 it is w.x.y.128/28. So your available addresses are 129-142. I suggest to configure the inside interface with a fix address, for example w.x.y.129/28, this address is then used as default-gateway for your inside computers. Then you change your nat source list from access-list 121 to a number between 1-99, for example access-list 21 permit w.x.y.128/28. Because many reports that there are problems with nat and access-list using any any.
For the backup interface, I'm not sure what C1101 supports, so I give two example. First, if you wan't to use vlan 1, then you have to make the g0/1/0 and g0/1/1 a switchport, I think it's a routed port by default. This is done with the command "switchport" followed by "switchport mode access" under respective interface. If this is not supported, you can try to remove interface vlan1, and configure a "interface BVI 1" instead. Complete configuration is explained here by @peter.paluch
https://community.cisco.com/t5/switching/bvi-what-is-it-and-what-are-its-uses/td-p/2373489
