That is all without me taking any tax from them - if I taxed them the growth rate would be lower. In fact, if anything I have probably cut them back too much and might increase their income slightly before release.
Trade Good Changes
The base production of Trade Goods is halved. In addition, the production is multiplied by the manufacturing percentage of the colony, so smaller colonies will generally produce more trade goods per capita. For a homeworld, trade good production is likely to be about 1/8th of the existing level (halved and then multiplied by 25%).
Maybe scale back trade goods production to 1/4th of the 2.5 level (Just manufacturing percentage) and set Default Tax level twice as high to compensate and make the baseline shipping line income & growth the same (as in your test game)?
That will give all players more flexibility to experiment with tax vs growth in both directions + cater to players that don't mind the performance impact of having a bit larger shipping lines (with the downside of higher tax from shipping if balance is off).
That or expose a modifier for base production of Trade Goods to starting game setup.