Can donation forms have suggested giving amounts and an "other" option?

You may setup your form to suggest amounts and have other options.

First, you can assign values to your options.

Guide:https://www.jotform.com/help/301-How-to-Assign-Calculation-Value

Second, you can pass your values and calculations to your Payment Field.

Guide:https://www.jotform.com/help/275-How-to-Pass-a-Calculation-to-a-Payment-Field

Hope this information helps.

Please give it a try and let us know if this fits your requirements.