Dont give up your efforts, modding an engine is not an easy thing, especially at first, but once you can make consistent grinds and clean mods, just the appearance alone of your work will be very satisfying. Of course, modding the passages in any block, side exhaust or rear exhaust, is always very hard. Even professional modders have to turn their Dremelling tools into contortion artists to get at those internal passageways.

As for the port mods, continue and go with what you described and make small cuts, and feel free to ocasionally test fit everthing and even semi-assemble the engine (reinstalling the crank, conrod, piston, and modded sleeve) and use the degree wheel to check your progress. That way, you will be certain that you are not overcutting the ports to a duration that is too high. It is better to make tiny cuts and view your work after each tiny cut and slowly progress as you go along, that way, you get steadier hands and moe experience in improving your Dremeling skills. Of course, prior to test fitting the prgression of your parts, clean them off to prevent the parts marring and scrubbing from the ginding shards and metal bits.

As for your fuel pooling like you are mentioning, the turbo cuts on the crank can help distribute the fule into the air more evenly , this should help with reducing the pooling and even help in ful economy and better power output the fuel-air will burn more completely since they are better mixed.

If you want to better your modding skills before you do any big mods on your engine, if you can get a hold of work out sleeves (or have some laying around from prior rebuilds) or get a hold of some junk engines, practice on those to further improve your dremelling and modding skills so you dont have to be afraid ruining a perfectly good engine.

As a hobby modder myself, I truely believe that anyone can learn to successfully mod their engines with enough practice. Though we hobby modders may never become the master artisans that reputable professional modders are, I believe that we hobby modders can in some cases come close.