The safety features of all the hydraulic presses I have seen are contained within the bottle jack in the form of an over-pressure safety valve. Finished steel tube, rod, bar and plate, ready for fabrication and at all sizes, are generally available for about $2/lb if you look around. It can be as low as $1/lb for short pieces and remnants, and as high as $3-4/lb at a high point if you pay for cutting, etc. The steel for this press can fall in below $200.
Re: Having a skilled brother welder, I’ll give you that, I am lucky 